Add nullable annotations to SignalR.Common, SignalR.Core and Http.Connections (#24764)

* Add nullable annotations to  SignalR.Common, SignalR.Core and Http.Connections

Contributes to https://github.com/dotnet/aspnetcore/issues/5680

* Changes per PR comments. Also add nullability to hub protocols

src/Servers/Connections.Abstractions/src/BaseConnectionContext.cs

@@ -15,7 +15,7 @@ namespace Microsoft.AspNetCore.Connections
         /// <summary>
         /// Gets or sets a unique identifier to represent this connection in trace logs.
         /// </summary>
-        public abstract string? ConnectionId { get; set; }
+        public abstract string ConnectionId { get; set; }
 
         /// <summary>
         /// Gets the collection of features provided by the server and middleware available on this connection.
@@ -25,7 +25,7 @@ namespace Microsoft.AspNetCore.Connections
         /// <summary>
         /// Gets or sets a key/value collection that can be used to share data within the scope of this connection.
         /// </summary>
-        public abstract IDictionary<object, object?>? Items { get; set; }
+        public abstract IDictionary<object, object?> Items { get; set; }
 
         /// <summary>
         /// Triggered when the client connection is closed.

src/Servers/Connections.Abstractions/src/ConnectionContext.cs

@@ -15,7 +15,7 @@ namespace Microsoft.AspNetCore.Connections
         /// <summary>
         /// Gets or sets the <see cref="IDuplexPipe"/> that can be used to read or write data on this connection.
         /// </summary>
-        public abstract IDuplexPipe? Transport { get; set; }
+        public abstract IDuplexPipe Transport { get; set; }
 
         /// <summary>
         /// Aborts the underlying connection.

src/Servers/Connections.Abstractions/src/DefaultConnectionContext.cs

@@ -55,17 +55,17 @@ namespace Microsoft.AspNetCore.Connections
             Application = application;
         }
 
-        public override string? ConnectionId { get; set; }
+        public override string ConnectionId { get; set; }
 
         public override IFeatureCollection Features { get; }
 
         public ClaimsPrincipal? User { get; set; }
 
-        public override IDictionary<object, object?>? Items { get; set; } = new ConnectionItems();
+        public override IDictionary<object, object?> Items { get; set; } = new ConnectionItems();
 
         public IDuplexPipe? Application { get; set; }
 
-        public override IDuplexPipe? Transport { get; set; }
+        public override IDuplexPipe Transport { get; set; } = default!;
 
         public override CancellationToken ConnectionClosed { get; set; }
         public override EndPoint? LocalEndPoint { get; set; }

src/Servers/Connections.Abstractions/src/Features/IConnectionIdFeature.cs

@@ -5,6 +5,6 @@ namespace Microsoft.AspNetCore.Connections.Features
 {
     public interface IConnectionIdFeature
     {
-        string? ConnectionId { get; set; }
+        string ConnectionId { get; set; }
     }
 }

src/Servers/Connections.Abstractions/src/Features/IConnectionItemsFeature.cs

@@ -7,6 +7,6 @@ namespace Microsoft.AspNetCore.Connections.Features
 {
     public interface IConnectionItemsFeature
     {
-        IDictionary<object, object?>? Items { get; set; }
+        IDictionary<object, object?> Items { get; set; }
     }
 }

src/Servers/Connections.Abstractions/src/Features/IConnectionTransportFeature.cs

@@ -7,6 +7,6 @@ namespace Microsoft.AspNetCore.Connections.Features
 {
     public interface IConnectionTransportFeature
     {
-        IDuplexPipe? Transport { get; set; }
+        IDuplexPipe Transport { get; set; }
     }
 }

src/Shared/ObjectMethodExecutor/AwaitableInfo.cs

@@ -1,6 +1,8 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
+#nullable disable
+
 using System;
 using System.Linq;
 using System.Reflection;

src/Shared/ObjectMethodExecutor/CoercedAwaitableInfo.cs

@@ -1,6 +1,8 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
+#nullable disable
+
 using System;
 using System.Linq.Expressions;
 

src/Shared/ObjectMethodExecutor/ObjectMethodExecutor.cs

@@ -1,6 +1,8 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
+#nullable disable
+
 using System;
 using System.Collections.Generic;
 using System.Linq.Expressions;

src/Shared/ObjectMethodExecutor/ObjectMethodExecutorAwaitable.cs

@@ -1,6 +1,8 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
+#nullable disable
+
 using System;
 using System.Runtime.CompilerServices;
 

src/Shared/ObjectMethodExecutor/ObjectMethodExecutorFSharpSupport.cs

@@ -1,6 +1,8 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
+#nullable disable
+
 using System;
 using System.Linq;
 using System.Linq.Expressions;

src/SignalR/common/Http.Connections/src/ConnectionEndpointRouteBuilderExtensions.cs

@@ -43,7 +43,7 @@ namespace Microsoft.AspNetCore.Builder
         /// <param name="pattern">The route pattern.</param>
         /// <param name="configureOptions">A callback to configure dispatcher options.</param>
         /// <returns>An <see cref="ConnectionEndpointRouteBuilder"/> for endpoints associated with the connections.</returns>
-        public static ConnectionEndpointRouteBuilder MapConnectionHandler<TConnectionHandler>(this IEndpointRouteBuilder endpoints, string pattern, Action<HttpConnectionDispatcherOptions> configureOptions) where TConnectionHandler : ConnectionHandler
+        public static ConnectionEndpointRouteBuilder MapConnectionHandler<TConnectionHandler>(this IEndpointRouteBuilder endpoints, string pattern, Action<HttpConnectionDispatcherOptions>? configureOptions) where TConnectionHandler : ConnectionHandler
         {
             var options = new HttpConnectionDispatcherOptions();
             configureOptions?.Invoke(options);

src/SignalR/common/Http.Connections/src/HttpConnectionContextExtensions.cs

@@ -18,7 +18,7 @@ namespace Microsoft.AspNetCore.Http.Connections
         /// SignalR connections can run on top of HTTP transports like WebSockets or Long Polling, or other non-HTTP transports. As a result,
         /// this method can sometimes return <see langword="null"/> depending on the configuration of your application.
         /// </remarks>
-        public static HttpContext GetHttpContext(this ConnectionContext connection)
+        public static HttpContext? GetHttpContext(this ConnectionContext connection)
         {
             return connection.Features.Get<IHttpContextFeature>()?.HttpContext;
         }

src/SignalR/common/Http.Connections/src/Internal/ConnectionLogScope.cs

@@ -1,6 +1,8 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
+#nullable disable
+
 using System;
 using System.Collections;
 using System.Collections.Generic;

src/SignalR/common/Http.Connections/src/Internal/HttpConnectionContext.cs

@@ -1,6 +1,8 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
+#nullable disable
+
 using System;
 using System.Collections.Concurrent;
 using System.Collections.Generic;

src/SignalR/common/Http.Connections/src/Internal/HttpConnectionDispatcher.Log.cs

@@ -10,52 +10,52 @@ namespace Microsoft.AspNetCore.Http.Connections.Internal
     {
         internal static class Log
         {
-            private static readonly Action<ILogger, string, Exception> _connectionDisposed =
+            private static readonly Action<ILogger, string, Exception?> _connectionDisposed =
                 LoggerMessage.Define<string>(LogLevel.Debug, new EventId(1, "ConnectionDisposed"), "Connection {TransportConnectionId} was disposed.");
 
-            private static readonly Action<ILogger, string, string, Exception> _connectionAlreadyActive =
+            private static readonly Action<ILogger, string, string, Exception?> _connectionAlreadyActive =
                 LoggerMessage.Define<string, string>(LogLevel.Debug, new EventId(2, "ConnectionAlreadyActive"), "Connection {TransportConnectionId} is already active via {RequestId}.");
 
-            private static readonly Action<ILogger, string, string, Exception> _pollCanceled =
+            private static readonly Action<ILogger, string, string, Exception?> _pollCanceled =
                 LoggerMessage.Define<string, string>(LogLevel.Trace, new EventId(3, "PollCanceled"), "Previous poll canceled for {TransportConnectionId} on {RequestId}.");
 
-            private static readonly Action<ILogger, Exception> _establishedConnection =
+            private static readonly Action<ILogger, Exception?> _establishedConnection =
                 LoggerMessage.Define(LogLevel.Debug, new EventId(4, "EstablishedConnection"), "Establishing new connection.");
 
-            private static readonly Action<ILogger, Exception> _resumingConnection =
+            private static readonly Action<ILogger, Exception?> _resumingConnection =
                 LoggerMessage.Define(LogLevel.Debug, new EventId(5, "ResumingConnection"), "Resuming existing connection.");
 
-            private static readonly Action<ILogger, long, Exception> _receivedBytes =
+            private static readonly Action<ILogger, long, Exception?> _receivedBytes =
                 LoggerMessage.Define<long>(LogLevel.Trace, new EventId(6, "ReceivedBytes"), "Received {Count} bytes.");
 
-            private static readonly Action<ILogger, HttpTransportType, Exception> _transportNotSupported =
+            private static readonly Action<ILogger, HttpTransportType, Exception?> _transportNotSupported =
                 LoggerMessage.Define<HttpTransportType>(LogLevel.Debug, new EventId(7, "TransportNotSupported"), "{TransportType} transport not supported by this connection handler.");
 
-            private static readonly Action<ILogger, HttpTransportType, HttpTransportType, Exception> _cannotChangeTransport =
+            private static readonly Action<ILogger, HttpTransportType, HttpTransportType, Exception?> _cannotChangeTransport =
                 LoggerMessage.Define<HttpTransportType, HttpTransportType>(LogLevel.Debug, new EventId(8, "CannotChangeTransport"), "Cannot change transports mid-connection; currently using {TransportType}, requesting {RequestedTransport}.");
 
-            private static readonly Action<ILogger, Exception> _postNotallowedForWebsockets =
+            private static readonly Action<ILogger, Exception?> _postNotallowedForWebsockets =
                 LoggerMessage.Define(LogLevel.Debug, new EventId(9, "PostNotAllowedForWebSockets"), "POST requests are not allowed for websocket connections.");
 
-            private static readonly Action<ILogger, Exception> _negotiationRequest =
+            private static readonly Action<ILogger, Exception?> _negotiationRequest =
                 LoggerMessage.Define(LogLevel.Debug, new EventId(10, "NegotiationRequest"), "Sending negotiation response.");
 
-            private static readonly Action<ILogger, HttpTransportType, Exception> _receivedDeleteRequestForUnsupportedTransport =
+            private static readonly Action<ILogger, HttpTransportType, Exception?> _receivedDeleteRequestForUnsupportedTransport =
                 LoggerMessage.Define<HttpTransportType>(LogLevel.Trace, new EventId(11, "ReceivedDeleteRequestForUnsupportedTransport"), "Received DELETE request for unsupported transport: {TransportType}.");
 
-            private static readonly Action<ILogger, Exception> _terminatingConnection =
+            private static readonly Action<ILogger, Exception?> _terminatingConnection =
                 LoggerMessage.Define(LogLevel.Trace, new EventId(12, "TerminatingConection"), "Terminating Long Polling connection due to a DELETE request.");
 
-            private static readonly Action<ILogger, string, Exception> _connectionDisposedWhileWriteInProgress =
+            private static readonly Action<ILogger, string, Exception?> _connectionDisposedWhileWriteInProgress =
                 LoggerMessage.Define<string>(LogLevel.Debug, new EventId(13, "ConnectionDisposedWhileWriteInProgress"), "Connection {TransportConnectionId} was disposed while a write was in progress.");
 
-            private static readonly Action<ILogger, string, Exception> _failedToReadHttpRequestBody =
+            private static readonly Action<ILogger, string, Exception?> _failedToReadHttpRequestBody =
                 LoggerMessage.Define<string>(LogLevel.Debug, new EventId(14, "FailedToReadHttpRequestBody"), "Connection {TransportConnectionId} failed to read the HTTP request body.");
 
-            private static readonly Action<ILogger, int, Exception> _negotiateProtocolVersionMismatch =
+            private static readonly Action<ILogger, int, Exception?> _negotiateProtocolVersionMismatch =
                 LoggerMessage.Define<int>(LogLevel.Debug, new EventId(15, "NegotiateProtocolVersionMismatch"), "The client requested version '{clientProtocolVersion}', but the server does not support this version.");
 
-            private static readonly Action<ILogger, string, Exception> _invalidNegotiateProtocolVersion =
+            private static readonly Action<ILogger, string, Exception?> _invalidNegotiateProtocolVersion =
                LoggerMessage.Define<string>(LogLevel.Debug, new EventId(16, "InvalidNegotiateProtocolVersion"), "The client requested an invalid protocol version '{queryStringVersionValue}'");
 
             public static void ConnectionDisposed(ILogger logger, string connectionId)

src/SignalR/common/Http.Connections/src/Internal/HttpConnectionDispatcher.cs

@@ -1,6 +1,8 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
+#nullable disable
+
 using System;
 using System.Buffers;
 using System.Collections.Generic;

src/SignalR/common/Http.Connections/src/Internal/HttpConnectionManager.Log.cs

@@ -10,32 +10,32 @@ namespace Microsoft.AspNetCore.Http.Connections.Internal
     {
         private static class Log
         {
-            private static readonly Action<ILogger, string, Exception> _createdNewConnection =
+            private static readonly Action<ILogger, string, Exception?> _createdNewConnection =
                 LoggerMessage.Define<string>(LogLevel.Debug, new EventId(1, "CreatedNewConnection"), "New connection {TransportConnectionId} created.");
 
-            private static readonly Action<ILogger, string, Exception> _removedConnection =
+            private static readonly Action<ILogger, string, Exception?> _removedConnection =
                 LoggerMessage.Define<string>(LogLevel.Debug, new EventId(2, "RemovedConnection"), "Removing connection {TransportConnectionId} from the list of connections.");
 
-            private static readonly Action<ILogger, string, Exception> _failedDispose =
+            private static readonly Action<ILogger, string, Exception?> _failedDispose =
                 LoggerMessage.Define<string>(LogLevel.Error, new EventId(3, "FailedDispose"), "Failed disposing connection {TransportConnectionId}.");
 
-            private static readonly Action<ILogger, string, Exception> _connectionReset =
+            private static readonly Action<ILogger, string, Exception?> _connectionReset =
                 LoggerMessage.Define<string>(LogLevel.Trace, new EventId(4, "ConnectionReset"), "Connection {TransportConnectionId} was reset.");
 
-            private static readonly Action<ILogger, string, Exception> _connectionTimedOut =
+            private static readonly Action<ILogger, string, Exception?> _connectionTimedOut =
                 LoggerMessage.Define<string>(LogLevel.Trace, new EventId(5, "ConnectionTimedOut"), "Connection {TransportConnectionId} timed out.");
 
             // 6, ScanningConnections - removed
 
-            private static readonly Action<ILogger, Exception> _scanningConnectionsFailed =
+            private static readonly Action<ILogger, Exception?> _scanningConnectionsFailed =
                 LoggerMessage.Define(LogLevel.Error, new EventId(7, "ScanningConnectionsFailed"), "Scanning connections failed.");
 
             // 8, ScannedConnections - removed
 
-            private static readonly Action<ILogger, Exception> _heartbeatStarted =
+            private static readonly Action<ILogger, Exception?> _heartbeatStarted =
                 LoggerMessage.Define(LogLevel.Trace, new EventId(9, "HeartBeatStarted"), "Starting connection heartbeat.");
 
-            private static readonly Action<ILogger, Exception> _heartbeatEnded =
+            private static readonly Action<ILogger, Exception?> _heartbeatEnded =
                 LoggerMessage.Define(LogLevel.Trace, new EventId(10, "HeartBeatEnded"), "Ending connection heartbeat.");
 
             public static void CreatedNewConnection(ILogger logger, string connectionId)

src/SignalR/common/Http.Connections/src/Internal/HttpConnectionManager.cs

@@ -5,6 +5,7 @@ using System;
 using System.Collections.Concurrent;
 using System.Collections.Generic;
 using System.Diagnostics;
+using System.Diagnostics.CodeAnalysis;
 using System.IO;
 using System.IO.Pipelines;
 using System.Net.WebSockets;
@@ -50,7 +51,7 @@ namespace Microsoft.AspNetCore.Http.Connections.Internal
             _ = ExecuteTimerLoop();
         }
 
-        internal bool TryGetConnection(string id, out HttpConnectionContext connection)
+        internal bool TryGetConnection(string id, [NotNullWhen(true)] out HttpConnectionContext? connection)
         {
             connection = null;
 

src/SignalR/common/Http.Connections/src/Internal/HttpConnectionsEventSource.cs

@@ -1,6 +1,8 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
+#nullable disable
+
 using System.Diagnostics.Tracing;
 using System.Threading;
 using Microsoft.Extensions.Internal;

src/SignalR/common/Http.Connections/src/Internal/Transports/LongPollingServerTransport.cs

@@ -16,13 +16,13 @@ namespace Microsoft.AspNetCore.Http.Connections.Internal.Transports
         private readonly PipeReader _application;
         private readonly ILogger _logger;
         private readonly CancellationToken _timeoutToken;
-        private readonly HttpConnectionContext _connection;
+        private readonly HttpConnectionContext? _connection;
 
         public LongPollingServerTransport(CancellationToken timeoutToken, PipeReader application, ILoggerFactory loggerFactory)
             : this(timeoutToken, application, loggerFactory, connection: null)
         { }
 
-        public LongPollingServerTransport(CancellationToken timeoutToken, PipeReader application, ILoggerFactory loggerFactory, HttpConnectionContext connection)
+        public LongPollingServerTransport(CancellationToken timeoutToken, PipeReader application, ILoggerFactory loggerFactory, HttpConnectionContext? connection)
         {
             _timeoutToken = timeoutToken;
             _application = application;
@@ -117,19 +117,19 @@ namespace Microsoft.AspNetCore.Http.Connections.Internal.Transports
 
         private static class Log
         {
-            private static readonly Action<ILogger, Exception> _longPolling204 =
+            private static readonly Action<ILogger, Exception?> _longPolling204 =
                 LoggerMessage.Define(LogLevel.Debug, new EventId(1, "LongPolling204"), "Terminating Long Polling connection by sending 204 response.");
 
-            private static readonly Action<ILogger, Exception> _pollTimedOut =
+            private static readonly Action<ILogger, Exception?> _pollTimedOut =
                 LoggerMessage.Define(LogLevel.Debug, new EventId(2, "PollTimedOut"), "Poll request timed out. Sending 200 response to connection.");
 
-            private static readonly Action<ILogger, long, Exception> _longPollingWritingMessage =
+            private static readonly Action<ILogger, long, Exception?> _longPollingWritingMessage =
                 LoggerMessage.Define<long>(LogLevel.Trace, new EventId(3, "LongPollingWritingMessage"), "Writing a {Count} byte message to connection.");
 
-            private static readonly Action<ILogger, Exception> _longPollingDisconnected =
+            private static readonly Action<ILogger, Exception?> _longPollingDisconnected =
                 LoggerMessage.Define(LogLevel.Debug, new EventId(4, "LongPollingDisconnected"), "Client disconnected from Long Polling endpoint for connection.");
 
-            private static readonly Action<ILogger, Exception> _longPollingTerminated =
+            private static readonly Action<ILogger, Exception?> _longPollingTerminated =
                 LoggerMessage.Define(LogLevel.Error, new EventId(5, "LongPollingTerminated"), "Long Polling transport was terminated due to an error on connection.");
 
             public static void LongPolling204(ILogger logger)

src/SignalR/common/Http.Connections/src/Internal/Transports/ServerSentEventsServerTransport.cs

@@ -16,13 +16,13 @@ namespace Microsoft.AspNetCore.Http.Connections.Internal.Transports
         private readonly PipeReader _application;
         private readonly string _connectionId;
         private readonly ILogger _logger;
-        private readonly HttpConnectionContext _connection;
+        private readonly HttpConnectionContext? _connection;
 
         public ServerSentEventsServerTransport(PipeReader application, string connectionId, ILoggerFactory loggerFactory)
             : this(application, connectionId, connection: null, loggerFactory)
         { }
 
-        public ServerSentEventsServerTransport(PipeReader application, string connectionId, HttpConnectionContext connection, ILoggerFactory loggerFactory)
+        public ServerSentEventsServerTransport(PipeReader application, string connectionId, HttpConnectionContext? connection, ILoggerFactory loggerFactory)
         {
             _application = application;
             _connectionId = connectionId;
@@ -90,7 +90,7 @@ namespace Microsoft.AspNetCore.Http.Connections.Internal.Transports
 
         private static class Log
         {
-            private static readonly Action<ILogger, long, Exception> _sseWritingMessage =
+            private static readonly Action<ILogger, long, Exception?> _sseWritingMessage =
                 LoggerMessage.Define<long>(LogLevel.Trace, new EventId(1, "SSEWritingMessage"), "Writing a {Count} byte message.");
 
             public static void SSEWritingMessage(ILogger logger, long count)

src/SignalR/common/Http.Connections/src/Internal/Transports/WebSocketsServerTransport.Log.cs

@@ -11,51 +11,51 @@ namespace Microsoft.AspNetCore.Http.Connections.Internal.Transports
     {
         private static class Log
         {
-            private static readonly Action<ILogger, string, Exception> _socketOpened =
-                LoggerMessage.Define<string>(LogLevel.Debug, new EventId(1, "SocketOpened"), "Socket opened using Sub-Protocol: '{SubProtocol}'.");
+            private static readonly Action<ILogger, string?, Exception?> _socketOpened =
+                LoggerMessage.Define<string?>(LogLevel.Debug, new EventId(1, "SocketOpened"), "Socket opened using Sub-Protocol: '{SubProtocol}'.");
 
-            private static readonly Action<ILogger, Exception> _socketClosed =
+            private static readonly Action<ILogger, Exception?> _socketClosed =
                 LoggerMessage.Define(LogLevel.Debug, new EventId(2, "SocketClosed"), "Socket closed.");
 
-            private static readonly Action<ILogger, WebSocketCloseStatus?, string, Exception> _clientClosed =
+            private static readonly Action<ILogger, WebSocketCloseStatus?, string, Exception?> _clientClosed =
                 LoggerMessage.Define<WebSocketCloseStatus?, string>(LogLevel.Debug, new EventId(3, "ClientClosed"), "Client closed connection with status code '{Status}' ({Description}). Signaling end-of-input to application.");
 
-            private static readonly Action<ILogger, Exception> _waitingForSend =
+            private static readonly Action<ILogger, Exception?> _waitingForSend =
                 LoggerMessage.Define(LogLevel.Debug, new EventId(4, "WaitingForSend"), "Waiting for the application to finish sending data.");
 
-            private static readonly Action<ILogger, Exception> _failedSending =
+            private static readonly Action<ILogger, Exception?> _failedSending =
                 LoggerMessage.Define(LogLevel.Debug, new EventId(5, "FailedSending"), "Application failed during sending. Sending InternalServerError close frame.");
 
-            private static readonly Action<ILogger, Exception> _finishedSending =
+            private static readonly Action<ILogger, Exception?> _finishedSending =
                 LoggerMessage.Define(LogLevel.Debug, new EventId(6, "FinishedSending"), "Application finished sending. Sending close frame.");
 
-            private static readonly Action<ILogger, Exception> _waitingForClose =
+            private static readonly Action<ILogger, Exception?> _waitingForClose =
                 LoggerMessage.Define(LogLevel.Debug, new EventId(7, "WaitingForClose"), "Waiting for the client to close the socket.");
 
-            private static readonly Action<ILogger, Exception> _closeTimedOut =
+            private static readonly Action<ILogger, Exception?> _closeTimedOut =
                 LoggerMessage.Define(LogLevel.Debug, new EventId(8, "CloseTimedOut"), "Timed out waiting for client to send the close frame, aborting the connection.");
 
-            private static readonly Action<ILogger, WebSocketMessageType, int, bool, Exception> _messageReceived =
+            private static readonly Action<ILogger, WebSocketMessageType, int, bool, Exception?> _messageReceived =
                 LoggerMessage.Define<WebSocketMessageType, int, bool>(LogLevel.Trace, new EventId(9, "MessageReceived"), "Message received. Type: {MessageType}, size: {Size}, EndOfMessage: {EndOfMessage}.");
 
-            private static readonly Action<ILogger, int, Exception> _messageToApplication =
+            private static readonly Action<ILogger, int, Exception?> _messageToApplication =
                 LoggerMessage.Define<int>(LogLevel.Trace, new EventId(10, "MessageToApplication"), "Passing message to application. Payload size: {Size}.");
 
-            private static readonly Action<ILogger, long, Exception> _sendPayload =
+            private static readonly Action<ILogger, long, Exception?> _sendPayload =
                 LoggerMessage.Define<long>(LogLevel.Trace, new EventId(11, "SendPayload"), "Sending payload: {Size} bytes.");
 
-            private static readonly Action<ILogger, Exception> _errorWritingFrame =
+            private static readonly Action<ILogger, Exception?> _errorWritingFrame =
                 LoggerMessage.Define(LogLevel.Debug, new EventId(12, "ErrorWritingFrame"), "Error writing frame.");
 
             // 13, SendFailed - removed
 
-            private static readonly Action<ILogger, Exception> _closedPrematurely =
+            private static readonly Action<ILogger, Exception?> _closedPrematurely =
                 LoggerMessage.Define(LogLevel.Debug, new EventId(14, "ClosedPrematurely"), "Socket connection closed prematurely.");
 
-            private static readonly Action<ILogger, Exception> _closingWebSocketFailed =
+            private static readonly Action<ILogger, Exception?> _closingWebSocketFailed =
                 LoggerMessage.Define(LogLevel.Debug, new EventId(15, "ClosingWebSocketFailed"), "Closing webSocket failed.");
 
-            public static void SocketOpened(ILogger logger, string subProtocol)
+            public static void SocketOpened(ILogger logger, string? subProtocol)
             {
                 _socketOpened(logger, subProtocol, null);
             }

src/SignalR/common/Http.Connections/src/Internal/Transports/WebSocketsServerTransport.cs

@@ -201,7 +201,7 @@ namespace Microsoft.AspNetCore.Http.Connections.Internal.Transports
 
         private async Task StartSending(WebSocket socket)
         {
-            Exception error = null;
+            Exception? error = null;
 
             try
             {

src/SignalR/common/Http.Connections/src/Microsoft.AspNetCore.Http.Connections.csproj

@@ -5,6 +5,7 @@
     <TargetFramework>$(DefaultNetCoreTargetFramework)</TargetFramework>
     <IsAspNetCoreApp>true</IsAspNetCoreApp>
     <IsPackable>false</IsPackable>
+    <Nullable>enable</Nullable>
   </PropertyGroup>
 
   <ItemGroup>

src/SignalR/common/Http.Connections/src/WebSocketOptions.cs

@@ -21,6 +21,6 @@ namespace Microsoft.AspNetCore.Http.Connections
         // WebSocketManager's list of sub protocols is an IList:
         // https://github.com/aspnet/HttpAbstractions/blob/a6bdb9b1ec6ed99978a508e71a7f131be7e4d9fb/src/Microsoft.AspNetCore.Http.Abstractions/WebSocketManager.cs#L23
         // Unfortunately, IList<T> does not implement IReadOnlyList<T> :(
-        public Func<IList<string>, string> SubProtocolSelector { get; set; }
+        public Func<IList<string>, string>? SubProtocolSelector { get; set; }
     }
 }

src/SignalR/common/Protocols.Json/src/Microsoft.AspNetCore.SignalR.Protocols.Json.csproj

@@ -7,6 +7,7 @@
     <IsAspNetCoreApp>true</IsAspNetCoreApp>
     <RootNamespace>Microsoft.AspNetCore.SignalR</RootNamespace>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
+    <Nullable>enable</Nullable>
   </PropertyGroup>
 
   <ItemGroup>

src/SignalR/common/Protocols.Json/src/Protocol/JsonHubProtocol.cs

@@ -1,6 +1,8 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
+#nullable disable
+
 using System;
 using System.Buffers;
 using System.Collections.Generic;

src/SignalR/common/Protocols.MessagePack/src/MessagePackHubProtocolOptions.cs

@@ -1,7 +1,6 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
-using System.Collections.Generic;
 using MessagePack;
 using Microsoft.AspNetCore.SignalR.Protocol;
 
@@ -9,7 +8,7 @@ namespace Microsoft.AspNetCore.SignalR
 {
     public class MessagePackHubProtocolOptions
     {
-        private MessagePackSerializerOptions _messagePackSerializerOptions;
+        private MessagePackSerializerOptions? _messagePackSerializerOptions;
 
         /// <summary>
         /// <para>Gets or sets the <see cref="MessagePackSerializerOptions"/> used internally by the <see cref="MessagePackSerializer" />.</para>

src/SignalR/common/Protocols.MessagePack/src/Microsoft.AspNetCore.SignalR.Protocols.MessagePack.csproj

@@ -5,6 +5,7 @@
     <TargetFramework>netstandard2.0</TargetFramework>
     <RootNamespace>Microsoft.AspNetCore.SignalR</RootNamespace>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
+    <Nullable>enable</Nullable>
   </PropertyGroup>
 
   <ItemGroup>

src/SignalR/common/Protocols.MessagePack/src/Protocol/MessagePackHubProtocol.cs

@@ -1,6 +1,8 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
+#nullable disable
+
 using System;
 using System.Buffers;
 using System.Collections.Generic;

src/SignalR/common/Protocols.NewtonsoftJson/src/Microsoft.AspNetCore.SignalR.Protocols.NewtonsoftJson.csproj

@@ -1,10 +1,11 @@
-<Project Sdk="Microsoft.NET.Sdk">
+<Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
     <Description>Implements the SignalR Hub Protocol using Newtonsoft.Json.</Description>
     <TargetFramework>netstandard2.0</TargetFramework>
     <RootNamespace>Microsoft.AspNetCore.SignalR</RootNamespace>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
+    <Nullable>enable</Nullable>
   </PropertyGroup>
 
   <ItemGroup>

src/SignalR/common/Protocols.NewtonsoftJson/src/Protocol/NewtonsoftJsonHubProtocol.cs

@@ -1,6 +1,8 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
+#nullable disable
+
 using System;
 using System.Buffers;
 using System.Collections.Generic;

src/SignalR/common/Shared/AsyncEnumerableAdapters.cs

@@ -1,6 +1,8 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
+#nullable disable
+
 using System.Collections.Generic;
 using System.Diagnostics;
 using System.Runtime.CompilerServices;

src/SignalR/common/Shared/MemoryBufferWriter.cs

@@ -1,6 +1,8 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
+#nullable disable
+
 using System;
 using System.Buffers;
 using System.Collections.Generic;

src/SignalR/common/Shared/PipeWriterStream.cs

@@ -1,6 +1,8 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
+#nullable disable
+
 using System.Buffers;
 using System.Threading;
 using System.Threading.Tasks;

src/SignalR/common/Shared/ReflectionHelper.cs

@@ -1,6 +1,8 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information. 
 
+#nullable disable
+
 using System;
 using System.Collections.Generic;
 using System.Linq;

src/SignalR/common/Shared/ReusableUtf8JsonWriter.cs

@@ -1,6 +1,8 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
+#nullable disable
+
 using System;
 using System.Buffers;
 using System.Text.Encodings.Web;

src/SignalR/common/Shared/SystemTextJsonExtensions.cs

@@ -1,6 +1,8 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
+#nullable enable
+
 using System.IO;
 using System.Text.Json;
 
@@ -69,7 +71,7 @@ namespace Microsoft.AspNetCore.Internal
             };
         }
 
-        public static string ReadAsString(this ref Utf8JsonReader reader, string propertyName)
+        public static string? ReadAsString(this ref Utf8JsonReader reader, string propertyName)
         {
             reader.Read();
 

src/SignalR/common/Shared/TimerAwaitable.cs

@@ -1,6 +1,8 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
+#nullable enable
+
 using System;
 using System.Runtime.CompilerServices;
 using System.Threading;
@@ -10,8 +12,8 @@ namespace Microsoft.AspNetCore.Internal
 {
     internal class TimerAwaitable : IDisposable, ICriticalNotifyCompletion
     {
-        private Timer _timer;
-        private Action _callback;
+        private Timer? _timer;
+        private Action? _callback;
         private static readonly Action _callbackCompleted = () => { };
 
         private readonly TimeSpan _period;
@@ -55,7 +57,7 @@ namespace Microsoft.AspNetCore.Internal
                             // If TimerAwaitable falls out of scope, the timer should be released.
                             _timer = new Timer(state =>
                             {
-                                var weakRef = (WeakReference<TimerAwaitable>)state;
+                                var weakRef = (WeakReference<TimerAwaitable>)state!;
                                 if (weakRef.TryGetTarget(out var thisRef))
                                 {
                                     thisRef.Tick();

src/SignalR/common/Shared/Utf8BufferTextReader.cs

@@ -1,6 +1,8 @@
-// Copyright (c) .NET Foundation. All rights reserved.
+// Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
+#nullable disable
+
 using System;
 using System.Buffers;
 using System.IO;

src/SignalR/common/Shared/Utf8BufferTextWriter.cs

@@ -1,6 +1,8 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
+#nullable disable
+
 using System;
 using System.Buffers;
 using System.Diagnostics;

src/SignalR/common/SignalR.Common/src/HubException.cs

@@ -28,7 +28,7 @@ namespace Microsoft.AspNetCore.SignalR
         /// with a specified error message.
         /// </summary>
         /// <param name="message">The error message that explains the reason for the exception.</param>
-        public HubException(string message) : base(message)
+        public HubException(string? message) : base(message)
         {
         }
 
@@ -38,7 +38,7 @@ namespace Microsoft.AspNetCore.SignalR
         /// </summary>
         /// <param name="message">The error message that explains the reason for the exception.</param>
         /// <param name="innerException">The exception that is the cause of the current exception, or <c>null</c> if no inner exception is specified.</param>
-        public HubException(string message, Exception innerException) : base(message, innerException)
+        public HubException(string? message, Exception? innerException) : base(message, innerException)
         {
         }
 

src/SignalR/common/SignalR.Common/src/Microsoft.AspNetCore.SignalR.Common.csproj

@@ -1,4 +1,4 @@
-<Project Sdk="Microsoft.NET.Sdk">
+<Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
     <Description>Common serialiation primitives for SignalR Clients Servers</Description>
@@ -7,6 +7,7 @@
     <IsAspNetCoreApp>true</IsAspNetCoreApp>
     <RootNamespace>Microsoft.AspNetCore.SignalR</RootNamespace>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
+    <Nullable>enable</Nullable>
   </PropertyGroup>
 
   <ItemGroup>

src/SignalR/common/SignalR.Common/src/Protocol/CloseMessage.cs

@@ -19,7 +19,7 @@ namespace Microsoft.AspNetCore.SignalR.Protocol
         /// <summary>
         /// Gets the optional error message.
         /// </summary>
-        public string Error { get; }
+        public string? Error { get; }
 
         /// <summary>
         /// If <see langword="false"/>, clients with automatic reconnects enabled should not attempt to automatically reconnect after receiving the <see cref="CloseMessage"/>.
@@ -30,7 +30,7 @@ namespace Microsoft.AspNetCore.SignalR.Protocol
         /// Initializes a new instance of the <see cref="CloseMessage"/> class with an optional error message and <see cref="AllowReconnect"/> set to <see langword="false"/>.
         /// </summary>
         /// <param name="error">An optional error message.</param>
-        public CloseMessage(string error)
+        public CloseMessage(string? error)
             : this(error, allowReconnect: false)
         {
         }
@@ -44,7 +44,7 @@ namespace Microsoft.AspNetCore.SignalR.Protocol
         /// <see langword="true"/>, if client with automatic reconnects enabled should attempt to reconnect after receiving the <see cref="CloseMessage"/>;
         /// <see langword="false"/>, if the client should not try to reconnect whether or not automatic reconnects are enabled.
         /// </param>
-        public CloseMessage(string error, bool allowReconnect)
+        public CloseMessage(string? error, bool allowReconnect)
         {
             Error = error;
             AllowReconnect = allowReconnect;

src/SignalR/common/SignalR.Common/src/Protocol/CompletionMessage.cs

@@ -2,17 +2,16 @@
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System;
-using System.Collections.Generic;
 
 namespace Microsoft.AspNetCore.SignalR.Protocol
 {
     public class CompletionMessage : HubInvocationMessage
     {
-        public string Error { get; }
-        public object Result { get; }
+        public string? Error { get; }
+        public object? Result { get; }
         public bool HasResult { get; }
 
-        public CompletionMessage(string invocationId, string error, object result, bool hasResult)
+        public CompletionMessage(string invocationId, string? error, object? result, bool hasResult)
             : base(invocationId)
         {
             if (error != null && result != null)

src/SignalR/common/SignalR.Common/src/Protocol/HandshakeProtocol.cs

@@ -5,6 +5,7 @@ using System;
 using System.Buffers;
 using System.Collections.Concurrent;
 using System.Diagnostics;
+using System.Diagnostics.CodeAnalysis;
 using System.IO;
 using System.Text;
 using System.Text.Json;
@@ -109,7 +110,7 @@ namespace Microsoft.AspNetCore.SignalR.Protocol
         /// <param name="buffer">The serialized representation of the message.</param>
         /// <param name="responseMessage">When this method returns, contains the parsed message.</param>
         /// <returns>A value that is <c>true</c> if the <see cref="HandshakeResponseMessage"/> was successfully parsed; otherwise, <c>false</c>.</returns>
-        public static bool TryParseResponseMessage(ref ReadOnlySequence<byte> buffer, out HandshakeResponseMessage responseMessage)
+        public static bool TryParseResponseMessage(ref ReadOnlySequence<byte> buffer, [NotNullWhen(true)] out HandshakeResponseMessage? responseMessage)
         {
             if (!TextMessageParser.TryParseMessage(ref buffer, out var payload))
             {
@@ -122,7 +123,7 @@ namespace Microsoft.AspNetCore.SignalR.Protocol
             reader.CheckRead();
             reader.EnsureObjectStart();
 
-            string error = null;
+            string? error = null;
 
             while (reader.CheckRead())
             {
@@ -163,7 +164,7 @@ namespace Microsoft.AspNetCore.SignalR.Protocol
         /// <param name="buffer">The serialized representation of the message.</param>
         /// <param name="requestMessage">When this method returns, contains the parsed message.</param>
         /// <returns>A value that is <c>true</c> if the <see cref="HandshakeRequestMessage"/> was successfully parsed; otherwise, <c>false</c>.</returns>
-        public static bool TryParseRequestMessage(ref ReadOnlySequence<byte> buffer, out HandshakeRequestMessage requestMessage)
+        public static bool TryParseRequestMessage(ref ReadOnlySequence<byte> buffer, [NotNullWhen(true)] out HandshakeRequestMessage? requestMessage)
         {
             if (!TextMessageParser.TryParseMessage(ref buffer, out var payload))
             {
@@ -176,7 +177,7 @@ namespace Microsoft.AspNetCore.SignalR.Protocol
             reader.CheckRead();
             reader.EnsureObjectStart();
 
-            string protocol = null;
+            string? protocol = null;
             int? protocolVersion = null;
 
             while (reader.CheckRead())

src/SignalR/common/SignalR.Common/src/Protocol/HandshakeRequestMessage.cs

@@ -1,4 +1,4 @@
-// Copyright (c) .NET Foundation. All rights reserved.
+// Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 namespace Microsoft.AspNetCore.SignalR.Protocol

src/SignalR/common/SignalR.Common/src/Protocol/HandshakeResponseMessage.cs

@@ -16,14 +16,14 @@ namespace Microsoft.AspNetCore.SignalR.Protocol
         /// <summary>
         /// Gets the optional error message.
         /// </summary>
-        public string Error { get; }
+        public string? Error { get; }
 
         /// <summary>
         /// Initializes a new instance of the <see cref="HandshakeResponseMessage"/> class.
         /// An error response does need a minor version. Since the handshake has failed, any extra data will be ignored.
         /// </summary>
         /// <param name="error">Error encountered by the server, indicating why the handshake has failed.</param>
-        public HandshakeResponseMessage(string error)
+        public HandshakeResponseMessage(string? error)
         {
             Error = error;
         }

src/SignalR/common/SignalR.Common/src/Protocol/HubInvocationMessage.cs

@@ -13,18 +13,18 @@ namespace Microsoft.AspNetCore.SignalR.Protocol
         /// <summary>
         /// Gets or sets a name/value collection of headers.
         /// </summary>
-        public IDictionary<string, string> Headers { get; set; }
+        public IDictionary<string, string>? Headers { get; set; }
 
         /// <summary>
         /// Gets the invocation ID.
         /// </summary>
-        public string InvocationId { get; }
+        public string? InvocationId { get; }
 
         /// <summary>
         /// Initializes a new instance of the <see cref="HubInvocationMessage"/> class.
         /// </summary>
         /// <param name="invocationId">The invocation ID.</param>
-        protected HubInvocationMessage(string invocationId)
+        protected HubInvocationMessage(string? invocationId)
         {
             InvocationId = invocationId;
         }

src/SignalR/common/SignalR.Common/src/Protocol/HubMethodInvocationMessage.cs

@@ -19,12 +19,12 @@ namespace Microsoft.AspNetCore.SignalR.Protocol
         /// <summary>
         /// Gets the target method arguments.
         /// </summary>
-        public object[] Arguments { get; }
+        public object?[]? Arguments { get; }
 
         /// <summary>
         /// The target methods stream IDs.
         /// </summary>
-        public string[] StreamIds { get; }
+        public string[]? StreamIds { get; }
 
         /// <summary>
         /// Initializes a new instance of the <see cref="HubMethodInvocationMessage"/> class.
@@ -33,7 +33,7 @@ namespace Microsoft.AspNetCore.SignalR.Protocol
         /// <param name="target">The target method name.</param>
         /// <param name="arguments">The target method arguments.</param>
         /// <param name="streamIds">The target methods stream IDs.</param>
-        protected HubMethodInvocationMessage(string invocationId, string target, object[] arguments, string[] streamIds)
+        protected HubMethodInvocationMessage(string? invocationId, string target, object?[]? arguments, string[]? streamIds)
             : this(invocationId, target, arguments)
         {
             StreamIds = streamIds;
@@ -45,7 +45,7 @@ namespace Microsoft.AspNetCore.SignalR.Protocol
         /// <param name="invocationId">The invocation ID.</param>
         /// <param name="target">The target method name.</param>
         /// <param name="arguments">The target method arguments.</param>
-        protected HubMethodInvocationMessage(string invocationId, string target, object[] arguments)
+        protected HubMethodInvocationMessage(string? invocationId, string target, object?[]? arguments)
             : base(invocationId)
         {
             if (string.IsNullOrEmpty(target))
@@ -68,7 +68,7 @@ namespace Microsoft.AspNetCore.SignalR.Protocol
         /// </summary>
         /// <param name="target">The target method name.</param>
         /// <param name="arguments">The target method arguments.</param>
-        public InvocationMessage(string target, object[] arguments)
+        public InvocationMessage(string target, object?[]? arguments)
             : this(null, target, arguments)
         {
         }
@@ -79,7 +79,7 @@ namespace Microsoft.AspNetCore.SignalR.Protocol
         /// <param name="invocationId">The invocation ID.</param>
         /// <param name="target">The target method name.</param>
         /// <param name="arguments">The target method arguments.</param>
-        public InvocationMessage(string invocationId, string target, object[] arguments)
+        public InvocationMessage(string? invocationId, string target, object?[]? arguments)
             : base(invocationId, target, arguments)
         {
         }
@@ -91,7 +91,7 @@ namespace Microsoft.AspNetCore.SignalR.Protocol
         /// <param name="target">The target method name.</param>
         /// <param name="arguments">The target method arguments.</param>
         /// <param name="streamIds">The target methods stream IDs.</param>
-        public InvocationMessage(string invocationId, string target, object[] arguments, string[] streamIds)
+        public InvocationMessage(string? invocationId, string target, object?[]? arguments, string[]? streamIds)
             : base(invocationId, target, arguments, streamIds)
         {
         }
@@ -103,7 +103,7 @@ namespace Microsoft.AspNetCore.SignalR.Protocol
             string streamIds;
             try
             {
-                args = string.Join(", ", Arguments?.Select(a => a?.ToString()));
+                args = Arguments == null ? string.Empty : string.Join(", ", Arguments.Select(a => a?.ToString()));
             }
             catch (Exception ex)
             {
@@ -158,7 +158,7 @@ namespace Microsoft.AspNetCore.SignalR.Protocol
             string streamIds;
             try
             {
-                args = string.Join(", ", Arguments?.Select(a => a?.ToString()));
+                args = Arguments == null ? string.Empty : string.Join(", ", Arguments.Select(a => a?.ToString()));
             }
             catch (Exception ex)
             {

src/SignalR/common/SignalR.Common/src/Protocol/IHubProtocol.cs

@@ -3,6 +3,7 @@
 
 using System;
 using System.Buffers;
+using System.Diagnostics.CodeAnalysis;
 using Microsoft.AspNetCore.Connections;
 
 namespace Microsoft.AspNetCore.SignalR.Protocol
@@ -34,7 +35,7 @@ namespace Microsoft.AspNetCore.SignalR.Protocol
         /// <param name="binder">The binder used to parse the message.</param>
         /// <param name="message">When this method returns <c>true</c>, contains the parsed message.</param>
         /// <returns>A value that is <c>true</c> if the <see cref="HubMessage"/> was successfully parsed; otherwise, <c>false</c>.</returns>
-        bool TryParseMessage(ref ReadOnlySequence<byte> input, IInvocationBinder binder, out HubMessage message);
+        bool TryParseMessage(ref ReadOnlySequence<byte> input, IInvocationBinder binder, [NotNullWhen(true)] out HubMessage message);
 
         /// <summary>
         /// Writes the specified <see cref="HubMessage"/> to a writer.

src/SignalR/common/SignalR.Common/src/Protocol/StreamItemMessage.cs

@@ -5,9 +5,9 @@ namespace Microsoft.AspNetCore.SignalR.Protocol
 {
     public class StreamItemMessage : HubInvocationMessage
     {
-        public object Item { get; }
+        public object? Item { get; }
 
-        public StreamItemMessage(string invocationId, object item) : base(invocationId)
+        public StreamItemMessage(string invocationId, object? item) : base(invocationId)
         {
             Item = item;
         }

src/SignalR/server/Core/src/ClientProxyExtensions.cs

@@ -34,7 +34,7 @@ namespace Microsoft.AspNetCore.SignalR
         /// <param name="arg1">The first argument.</param>
         /// <param name="cancellationToken">The token to monitor for cancellation requests. The default value is <see cref="CancellationToken.None" />.</param>
         /// <returns>A <see cref="Task"/> that represents the asynchronous invoke.</returns>
-        public static Task SendAsync(this IClientProxy clientProxy, string method, object arg1, CancellationToken cancellationToken = default)
+        public static Task SendAsync(this IClientProxy clientProxy, string method, object? arg1, CancellationToken cancellationToken = default)
         {
             return clientProxy.SendCoreAsync(method, new[] { arg1 }, cancellationToken);
         }
@@ -49,7 +49,7 @@ namespace Microsoft.AspNetCore.SignalR
         /// <param name="arg2">The second argument.</param>
         /// <param name="cancellationToken">The token to monitor for cancellation requests. The default value is <see cref="CancellationToken.None" />.</param>
         /// <returns>A <see cref="Task"/> that represents the asynchronous invoke.</returns>
-        public static Task SendAsync(this IClientProxy clientProxy, string method, object arg1, object arg2, CancellationToken cancellationToken = default)
+        public static Task SendAsync(this IClientProxy clientProxy, string method, object? arg1, object? arg2, CancellationToken cancellationToken = default)
         {
             return clientProxy.SendCoreAsync(method, new[] { arg1, arg2 }, cancellationToken);
         }
@@ -65,7 +65,7 @@ namespace Microsoft.AspNetCore.SignalR
         /// <param name="arg3">The third argument.</param>
         /// <param name="cancellationToken">The token to monitor for cancellation requests. The default value is <see cref="CancellationToken.None" />.</param>
         /// <returns>A <see cref="Task"/> that represents the asynchronous invoke.</returns>
-        public static Task SendAsync(this IClientProxy clientProxy, string method, object arg1, object arg2, object arg3, CancellationToken cancellationToken = default)
+        public static Task SendAsync(this IClientProxy clientProxy, string method, object? arg1, object? arg2, object? arg3, CancellationToken cancellationToken = default)
         {
             return clientProxy.SendCoreAsync(method, new[] { arg1, arg2, arg3 }, cancellationToken);
         }
@@ -82,7 +82,7 @@ namespace Microsoft.AspNetCore.SignalR
         /// <param name="arg4">The fourth argument.</param>
         /// <param name="cancellationToken">The token to monitor for cancellation requests. The default value is <see cref="CancellationToken.None" />.</param>
         /// <returns>A <see cref="Task"/> that represents the asynchronous invoke.</returns>
-        public static Task SendAsync(this IClientProxy clientProxy, string method, object arg1, object arg2, object arg3, object arg4, CancellationToken cancellationToken = default)
+        public static Task SendAsync(this IClientProxy clientProxy, string method, object? arg1, object? arg2, object? arg3, object? arg4, CancellationToken cancellationToken = default)
         {
             return clientProxy.SendCoreAsync(method, new[] { arg1, arg2, arg3, arg4 }, cancellationToken);
         }
@@ -100,7 +100,7 @@ namespace Microsoft.AspNetCore.SignalR
         /// <param name="arg5">The fifth argument.</param>
         /// <param name="cancellationToken">The token to monitor for cancellation requests. The default value is <see cref="CancellationToken.None" />.</param>
         /// <returns>A <see cref="Task"/> that represents the asynchronous invoke.</returns>
-        public static Task SendAsync(this IClientProxy clientProxy, string method, object arg1, object arg2, object arg3, object arg4, object arg5, CancellationToken cancellationToken = default)
+        public static Task SendAsync(this IClientProxy clientProxy, string method, object? arg1, object? arg2, object? arg3, object? arg4, object? arg5, CancellationToken cancellationToken = default)
         {
             return clientProxy.SendCoreAsync(method, new[] { arg1, arg2, arg3, arg4, arg5 }, cancellationToken);
         }
@@ -119,7 +119,7 @@ namespace Microsoft.AspNetCore.SignalR
         /// <param name="arg6">The sixth argument.</param>
         /// <param name="cancellationToken">The token to monitor for cancellation requests. The default value is <see cref="CancellationToken.None" />.</param>
         /// <returns>A <see cref="Task"/> that represents the asynchronous invoke.</returns>
-        public static Task SendAsync(this IClientProxy clientProxy, string method, object arg1, object arg2, object arg3, object arg4, object arg5, object arg6, CancellationToken cancellationToken = default)
+        public static Task SendAsync(this IClientProxy clientProxy, string method, object? arg1, object? arg2, object? arg3, object? arg4, object? arg5, object? arg6, CancellationToken cancellationToken = default)
         {
             return clientProxy.SendCoreAsync(method, new[] { arg1, arg2, arg3, arg4, arg5, arg6 }, cancellationToken);
         }
@@ -139,7 +139,7 @@ namespace Microsoft.AspNetCore.SignalR
         /// <param name="arg7">The seventh argument.</param>
         /// <param name="cancellationToken">The token to monitor for cancellation requests. The default value is <see cref="CancellationToken.None" />.</param>
         /// <returns>A <see cref="Task"/> that represents the asynchronous invoke.</returns>
-        public static Task SendAsync(this IClientProxy clientProxy, string method, object arg1, object arg2, object arg3, object arg4, object arg5, object arg6, object arg7, CancellationToken cancellationToken = default)
+        public static Task SendAsync(this IClientProxy clientProxy, string method, object? arg1, object? arg2, object? arg3, object? arg4, object? arg5, object? arg6, object? arg7, CancellationToken cancellationToken = default)
         {
             return clientProxy.SendCoreAsync(method, new[] { arg1, arg2, arg3, arg4, arg5, arg6, arg7 }, cancellationToken);
         }
@@ -160,7 +160,7 @@ namespace Microsoft.AspNetCore.SignalR
         /// <param name="arg8">The eigth argument.</param>
         /// <param name="cancellationToken">The token to monitor for cancellation requests. The default value is <see cref="CancellationToken.None" />.</param>
         /// <returns>A <see cref="Task"/> that represents the asynchronous invoke.</returns>
-        public static Task SendAsync(this IClientProxy clientProxy, string method, object arg1, object arg2, object arg3, object arg4, object arg5, object arg6, object arg7, object arg8, CancellationToken cancellationToken = default)
+        public static Task SendAsync(this IClientProxy clientProxy, string method, object? arg1, object? arg2, object? arg3, object? arg4, object? arg5, object? arg6, object? arg7, object? arg8, CancellationToken cancellationToken = default)
         {
             return clientProxy.SendCoreAsync(method, new[] { arg1, arg2, arg3, arg4, arg5, arg6, arg7, arg8 }, cancellationToken);
         }
@@ -182,7 +182,7 @@ namespace Microsoft.AspNetCore.SignalR
         /// <param name="arg9">The ninth argument.</param>
         /// <param name="cancellationToken">The token to monitor for cancellation requests. The default value is <see cref="CancellationToken.None" />.</param>
         /// <returns>A <see cref="Task"/> that represents the asynchronous invoke.</returns>
-        public static Task SendAsync(this IClientProxy clientProxy, string method, object arg1, object arg2, object arg3, object arg4, object arg5, object arg6, object arg7, object arg8, object arg9, CancellationToken cancellationToken = default)
+        public static Task SendAsync(this IClientProxy clientProxy, string method, object? arg1, object? arg2, object? arg3, object? arg4, object? arg5, object? arg6, object? arg7, object? arg8, object? arg9, CancellationToken cancellationToken = default)
         {
             return clientProxy.SendCoreAsync(method, new[] { arg1, arg2, arg3, arg4, arg5, arg6, arg7, arg8, arg9 }, cancellationToken);
         }
@@ -205,7 +205,7 @@ namespace Microsoft.AspNetCore.SignalR
         /// <param name="arg10">The tenth argument.</param>
         /// <param name="cancellationToken">The token to monitor for cancellation requests. The default value is <see cref="CancellationToken.None" />.</param>
         /// <returns>A <see cref="Task"/> that represents the asynchronous invoke.</returns>
-        public static Task SendAsync(this IClientProxy clientProxy, string method, object arg1, object arg2, object arg3, object arg4, object arg5, object arg6, object arg7, object arg8, object arg9, object arg10, CancellationToken cancellationToken = default)
+        public static Task SendAsync(this IClientProxy clientProxy, string method, object? arg1, object? arg2, object? arg3, object? arg4, object? arg5, object? arg6, object? arg7, object? arg8, object? arg9, object? arg10, CancellationToken cancellationToken = default)
         {
             return clientProxy.SendCoreAsync(method, new[] { arg1, arg2, arg3, arg4, arg5, arg6, arg7, arg8, arg9, arg10 }, cancellationToken);
         }

src/SignalR/server/Core/src/DefaultHubLifetimeManager.cs

@@ -80,15 +80,15 @@ namespace Microsoft.AspNetCore.SignalR
         }
 
         /// <inheritdoc />
-        public override Task SendAllAsync(string methodName, object[] args, CancellationToken cancellationToken = default)
+        public override Task SendAllAsync(string methodName, object?[]? args, CancellationToken cancellationToken = default)
         {
             return SendToAllConnections(methodName, args, include: null, state: null, cancellationToken);
         }
 
-        private Task SendToAllConnections(string methodName, object[] args, Func<HubConnectionContext, object, bool> include, object state = null, CancellationToken cancellationToken = default)
+        private Task SendToAllConnections(string methodName, object?[]? args, Func<HubConnectionContext, object?, bool>? include, object? state = null, CancellationToken cancellationToken = default)
         {
-            List<Task> tasks = null;
-            SerializedHubMessage message = null;
+            List<Task>? tasks = null;
+            SerializedHubMessage? message = null;
 
             // foreach over HubConnectionStore avoids allocating an enumerator
             foreach (var connection in _connections)
@@ -127,7 +127,7 @@ namespace Microsoft.AspNetCore.SignalR
 
         // Tasks and message are passed by ref so they can be lazily created inside the method post-filtering,
         // while still being re-usable when sending to multiple groups
-        private void SendToGroupConnections(string methodName, object[] args, ConcurrentDictionary<string, HubConnectionContext> connections, Func<HubConnectionContext, object, bool> include, object state, ref List<Task> tasks, ref SerializedHubMessage message, CancellationToken cancellationToken)
+        private void SendToGroupConnections(string methodName, object?[]? args, ConcurrentDictionary<string, HubConnectionContext> connections, Func<HubConnectionContext, object?, bool>? include, object? state, ref List<Task>? tasks, ref SerializedHubMessage? message, CancellationToken cancellationToken)
         {
             // foreach over ConcurrentDictionary avoids allocating an enumerator
             foreach (var connection in connections)
@@ -157,7 +157,7 @@ namespace Microsoft.AspNetCore.SignalR
         }
 
         /// <inheritdoc />
-        public override Task SendConnectionAsync(string connectionId, string methodName, object[] args, CancellationToken cancellationToken = default)
+        public override Task SendConnectionAsync(string connectionId, string methodName, object?[]? args, CancellationToken cancellationToken = default)
         {
             if (connectionId == null)
             {
@@ -179,7 +179,7 @@ namespace Microsoft.AspNetCore.SignalR
         }
 
         /// <inheritdoc />
-        public override Task SendGroupAsync(string groupName, string methodName, object[] args, CancellationToken cancellationToken = default)
+        public override Task SendGroupAsync(string groupName, string methodName, object?[]? args, CancellationToken cancellationToken = default)
         {
             if (groupName == null)
             {
@@ -191,8 +191,8 @@ namespace Microsoft.AspNetCore.SignalR
             {
                 // Can't optimize for sending to a single connection in a group because
                 // group might be modified inbetween checking and sending
-                List<Task> tasks = null;
-                SerializedHubMessage message = null;
+                List<Task>? tasks = null;
+                SerializedHubMessage? message = null;
                 SendToGroupConnections(methodName, args, group, null, null, ref tasks, ref message, cancellationToken);
 
                 if (tasks != null)
@@ -205,11 +205,11 @@ namespace Microsoft.AspNetCore.SignalR
         }
 
         /// <inheritdoc />
-        public override Task SendGroupsAsync(IReadOnlyList<string> groupNames, string methodName, object[] args, CancellationToken cancellationToken = default)
+        public override Task SendGroupsAsync(IReadOnlyList<string> groupNames, string methodName, object?[]? args, CancellationToken cancellationToken = default)
         {
             // Each task represents the list of tasks for each of the writes within a group
-            List<Task> tasks = null;
-            SerializedHubMessage message = null;
+            List<Task>? tasks = null;
+            SerializedHubMessage? message = null;
 
             foreach (var groupName in groupNames)
             {
@@ -234,7 +234,7 @@ namespace Microsoft.AspNetCore.SignalR
         }
 
         /// <inheritdoc />
-        public override Task SendGroupExceptAsync(string groupName, string methodName, object[] args, IReadOnlyList<string> excludedConnectionIds, CancellationToken cancellationToken = default)
+        public override Task SendGroupExceptAsync(string groupName, string methodName, object?[]? args, IReadOnlyList<string> excludedConnectionIds, CancellationToken cancellationToken = default)
         {
             if (groupName == null)
             {
@@ -244,10 +244,10 @@ namespace Microsoft.AspNetCore.SignalR
             var group = _groups[groupName];
             if (group != null)
             {
-                List<Task> tasks = null;
-                SerializedHubMessage message = null;
+                List<Task>? tasks = null;
+                SerializedHubMessage? message = null;
 
-                SendToGroupConnections(methodName, args, group, (connection, state) => !((IReadOnlyList<string>)state).Contains(connection.ConnectionId), excludedConnectionIds, ref tasks, ref message, cancellationToken);
+                SendToGroupConnections(methodName, args, group, (connection, state) => !((IReadOnlyList<string>)state!).Contains(connection.ConnectionId), excludedConnectionIds, ref tasks, ref message, cancellationToken);
 
                 if (tasks != null)
                 {
@@ -258,20 +258,20 @@ namespace Microsoft.AspNetCore.SignalR
             return Task.CompletedTask;
         }
 
-        private SerializedHubMessage CreateSerializedInvocationMessage(string methodName, object[] args)
+        private SerializedHubMessage CreateSerializedInvocationMessage(string methodName, object?[]? args)
         {
             return new SerializedHubMessage(CreateInvocationMessage(methodName, args));
         }
 
-        private HubMessage CreateInvocationMessage(string methodName, object[] args)
+        private HubMessage CreateInvocationMessage(string methodName, object?[]? args)
         {
             return new InvocationMessage(methodName, args);
         }
 
         /// <inheritdoc />
-        public override Task SendUserAsync(string userId, string methodName, object[] args, CancellationToken cancellationToken = default)
+        public override Task SendUserAsync(string userId, string methodName, object?[]? args, CancellationToken cancellationToken = default)
         {
-            return SendToAllConnections(methodName, args, (connection, state) => string.Equals(connection.UserIdentifier, (string)state, StringComparison.Ordinal), userId, cancellationToken);
+            return SendToAllConnections(methodName, args, (connection, state) => string.Equals(connection.UserIdentifier, (string)state!, StringComparison.Ordinal), userId, cancellationToken);
         }
 
         /// <inheritdoc />
@@ -290,21 +290,21 @@ namespace Microsoft.AspNetCore.SignalR
         }
 
         /// <inheritdoc />
-        public override Task SendAllExceptAsync(string methodName, object[] args, IReadOnlyList<string> excludedConnectionIds, CancellationToken cancellationToken = default)
+        public override Task SendAllExceptAsync(string methodName, object?[]? args, IReadOnlyList<string> excludedConnectionIds, CancellationToken cancellationToken = default)
         {
-            return SendToAllConnections(methodName, args, (connection, state) => !((IReadOnlyList<string>)state).Contains(connection.ConnectionId), excludedConnectionIds, cancellationToken);
+            return SendToAllConnections(methodName, args, (connection, state) => !((IReadOnlyList<string>)state!).Contains(connection.ConnectionId), excludedConnectionIds, cancellationToken);
         }
 
         /// <inheritdoc />
-        public override Task SendConnectionsAsync(IReadOnlyList<string> connectionIds, string methodName, object[] args, CancellationToken cancellationToken = default)
+        public override Task SendConnectionsAsync(IReadOnlyList<string> connectionIds, string methodName, object?[]? args, CancellationToken cancellationToken = default)
         {
-            return SendToAllConnections(methodName, args, (connection, state) => ((IReadOnlyList<string>)state).Contains(connection.ConnectionId), connectionIds, cancellationToken);
+            return SendToAllConnections(methodName, args, (connection, state) => ((IReadOnlyList<string>)state!).Contains(connection.ConnectionId), connectionIds, cancellationToken);
         }
 
         /// <inheritdoc />
-        public override Task SendUsersAsync(IReadOnlyList<string> userIds, string methodName, object[] args, CancellationToken cancellationToken = default)
+        public override Task SendUsersAsync(IReadOnlyList<string> userIds, string methodName, object?[]? args, CancellationToken cancellationToken = default)
         {
-            return SendToAllConnections(methodName, args, (connection, state) => ((IReadOnlyList<string>)state).Contains(connection.UserIdentifier), userIds, cancellationToken);
+            return SendToAllConnections(methodName, args, (connection, state) => ((IReadOnlyList<string>)state!).Contains(connection.UserIdentifier), userIds, cancellationToken);
         }
     }
 }

src/SignalR/server/Core/src/DefaultUserIdProvider.cs

@@ -1,4 +1,4 @@
-// Copyright (c) .NET Foundation. All rights reserved.
+// Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System.Security.Claims;
@@ -12,9 +12,9 @@ namespace Microsoft.AspNetCore.SignalR
     public class DefaultUserIdProvider : IUserIdProvider
     {
         /// <inheritdoc />
-        public virtual string GetUserId(HubConnectionContext connection)
+        public virtual string? GetUserId(HubConnectionContext connection)
         {
             return connection.User?.FindFirst(ClaimTypes.NameIdentifier)?.Value;
         }
     }
-}
+}

src/SignalR/server/Core/src/DynamicHub.cs

@@ -1,4 +1,4 @@
-// Copyright (c) .NET Foundation. All rights reserved.
+// Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 namespace Microsoft.AspNetCore.SignalR
@@ -8,7 +8,7 @@ namespace Microsoft.AspNetCore.SignalR
     /// </summary>
     public abstract class DynamicHub : Hub
     {
-        private DynamicHubClients _clients;
+        private DynamicHubClients? _clients;
 
         /// <summary>
         /// Gets or sets an object that can be used to invoke methods on the clients connected to this hub.

src/SignalR/server/Core/src/Hub.cs

@@ -12,9 +12,9 @@ namespace Microsoft.AspNetCore.SignalR
     public abstract class Hub : IDisposable
     {
         private bool _disposed;
-        private IHubCallerClients _clients;
-        private HubCallerContext _context;
-        private IGroupManager _groups;
+        private IHubCallerClients _clients = default!;
+        private HubCallerContext _context = default!;
+        private IGroupManager _groups = default!;
 
         /// <summary>
         /// Gets or sets an object that can be used to invoke methods on the clients connected to this hub.
@@ -80,7 +80,7 @@ namespace Microsoft.AspNetCore.SignalR
         /// Called when a connection with the hub is terminated.
         /// </summary>
         /// <returns>A <see cref="Task"/> that represents the asynchronous disconnect.</returns>
-        public virtual Task OnDisconnectedAsync(Exception exception)
+        public virtual Task OnDisconnectedAsync(Exception? exception)
         {
             return Task.CompletedTask;
         }

src/SignalR/server/Core/src/HubCallerContext.cs

@@ -21,17 +21,17 @@ namespace Microsoft.AspNetCore.SignalR
         /// <summary>
         /// Gets the user identifier.
         /// </summary>
-        public abstract string UserIdentifier { get; }
+        public abstract string? UserIdentifier { get; }
 
         /// <summary>
         /// Gets the user.
         /// </summary>
-        public abstract ClaimsPrincipal User { get; }
+        public abstract ClaimsPrincipal? User { get; }
 
         /// <summary>
         /// Gets a key/value collection that can be used to share data within the scope of this connection.
         /// </summary>
-        public abstract IDictionary<object, object> Items { get; }
+        public abstract IDictionary<object, object?> Items { get; }
 
         /// <summary>
         /// Gets the collection of HTTP features available on the connection.

src/SignalR/server/Core/src/HubConnectionContext.Log.cs

@@ -0,0 +1,97 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+#nullable disable
+
+using System;
+using Microsoft.Extensions.Logging;
+
+namespace Microsoft.AspNetCore.SignalR
+{
+    public partial class HubConnectionContext
+    {
+        private static class Log
+        {
+            // Category: HubConnectionContext
+            private static readonly Action<ILogger, string, Exception> _handshakeComplete =
+                LoggerMessage.Define<string>(LogLevel.Debug, new EventId(1, "HandshakeComplete"), "Completed connection handshake. Using HubProtocol '{Protocol}'.");
+
+            private static readonly Action<ILogger, Exception> _handshakeCanceled =
+                LoggerMessage.Define(LogLevel.Debug, new EventId(2, "HandshakeCanceled"), "Handshake was canceled.");
+
+            private static readonly Action<ILogger, Exception> _sentPing =
+                LoggerMessage.Define(LogLevel.Trace, new EventId(3, "SentPing"), "Sent a ping message to the client.");
+
+            private static readonly Action<ILogger, Exception> _transportBufferFull =
+                LoggerMessage.Define(LogLevel.Debug, new EventId(4, "TransportBufferFull"), "Unable to send Ping message to client, the transport buffer is full.");
+
+            private static readonly Action<ILogger, Exception> _handshakeFailed =
+                LoggerMessage.Define(LogLevel.Debug, new EventId(5, "HandshakeFailed"), "Failed connection handshake.");
+
+            private static readonly Action<ILogger, Exception> _failedWritingMessage =
+                LoggerMessage.Define(LogLevel.Error, new EventId(6, "FailedWritingMessage"), "Failed writing message. Aborting connection.");
+
+            private static readonly Action<ILogger, string, int, Exception> _protocolVersionFailed =
+                LoggerMessage.Define<string, int>(LogLevel.Debug, new EventId(7, "ProtocolVersionFailed"), "Server does not support version {Version} of the {Protocol} protocol.");
+
+            private static readonly Action<ILogger, Exception> _abortFailed =
+                LoggerMessage.Define(LogLevel.Trace, new EventId(8, "AbortFailed"), "Abort callback failed.");
+
+            private static readonly Action<ILogger, int, Exception> _clientTimeout =
+                LoggerMessage.Define<int>(LogLevel.Debug, new EventId(9, "ClientTimeout"), "Client timeout ({ClientTimeout}ms) elapsed without receiving a message from the client. Closing connection.");
+
+            private static readonly Action<ILogger, long, Exception> _handshakeSizeLimitExceeded =
+                LoggerMessage.Define<long>(LogLevel.Debug, new EventId(10, "HandshakeSizeLimitExceeded"), "The maximum message size of {MaxMessageSize}B was exceeded while parsing the Handshake. The message size can be configured in AddHubOptions.");
+
+            public static void HandshakeComplete(ILogger logger, string hubProtocol)
+            {
+                _handshakeComplete(logger, hubProtocol, null);
+            }
+
+            public static void HandshakeCanceled(ILogger logger)
+            {
+                _handshakeCanceled(logger, null);
+            }
+
+            public static void SentPing(ILogger logger)
+            {
+                _sentPing(logger, null);
+            }
+
+            public static void TransportBufferFull(ILogger logger)
+            {
+                _transportBufferFull(logger, null);
+            }
+
+            public static void HandshakeFailed(ILogger logger, Exception exception)
+            {
+                _handshakeFailed(logger, exception);
+            }
+
+            public static void FailedWritingMessage(ILogger logger, Exception exception)
+            {
+                _failedWritingMessage(logger, exception);
+            }
+
+            public static void ProtocolVersionFailed(ILogger logger, string protocolName, int version)
+            {
+                _protocolVersionFailed(logger, protocolName, version, null);
+            }
+
+            public static void AbortFailed(ILogger logger, Exception exception)
+            {
+                _abortFailed(logger, exception);
+            }
+
+            public static void ClientTimeout(ILogger logger, TimeSpan timeout)
+            {
+                _clientTimeout(logger, (int)timeout.TotalMilliseconds, null);
+            }
+
+            public static void HandshakeSizeLimitExceeded(ILogger logger, long maxMessageSize)
+            {
+                _handshakeSizeLimitExceeded(logger, maxMessageSize, null);
+            }
+        }
+    }
+}

src/SignalR/server/Core/src/HubConnectionContext.cs

@@ -23,9 +23,9 @@ namespace Microsoft.AspNetCore.SignalR
     /// <summary>
     /// Encapsulates all information about an individual connection to a SignalR Hub.
     /// </summary>
-    public class HubConnectionContext
+    public partial class HubConnectionContext
     {
-        private static readonly Action<object> _cancelReader = state => ((PipeReader)state).CancelPendingRead();
+        private static readonly Action<object?> _cancelReader = state => ((PipeReader)state!).CancelPendingRead();
         private static readonly WaitCallback _abortedCallback = AbortConnection;
 
         private readonly ConnectionContext _connectionContext;
@@ -39,7 +39,7 @@ namespace Microsoft.AspNetCore.SignalR
         private readonly ISystemClock _systemClock;
         private readonly CancellationTokenRegistration _closedRegistration;
 
-        private StreamTracker _streamTracker;
+        private StreamTracker? _streamTracker;
         private long _lastSendTimeStamp;
         private ReadOnlyMemory<byte> _cachedPingMessage;
         private bool _clientTimeoutActive;
@@ -67,7 +67,7 @@ namespace Microsoft.AspNetCore.SignalR
             _connectionContext = connectionContext;
             _logger = loggerFactory.CreateLogger<HubConnectionContext>();
             ConnectionAborted = _connectionAbortedTokenSource.Token;
-            _closedRegistration = connectionContext.ConnectionClosed.Register((state) => ((HubConnectionContext)state).Abort(), this);
+            _closedRegistration = connectionContext.ConnectionClosed.Register((state) => ((HubConnectionContext)state!).Abort(), this);
 
             HubCallerContext = new DefaultHubCallerContext(this);
 
@@ -91,7 +91,7 @@ namespace Microsoft.AspNetCore.SignalR
 
         internal HubCallerContext HubCallerContext { get; }
 
-        internal Exception CloseException { get; private set; }
+        internal Exception? CloseException { get; private set; }
 
         /// <summary>
         /// Gets a <see cref="CancellationToken"/> that notifies when the connection is aborted.
@@ -106,7 +106,7 @@ namespace Microsoft.AspNetCore.SignalR
         /// <summary>
         /// Gets the user for this connection.
         /// </summary>
-        public virtual ClaimsPrincipal User => Features.Get<IConnectionUserFeature>()?.User;
+        public virtual ClaimsPrincipal? User => Features.Get<IConnectionUserFeature>()?.User;
 
         /// <summary>
         /// Gets the collection of features available on this connection.
@@ -116,7 +116,7 @@ namespace Microsoft.AspNetCore.SignalR
         /// <summary>
         /// Gets a key/value collection that can be used to share data within the scope of this connection.
         /// </summary>
-        public virtual IDictionary<object, object> Items => _connectionContext.Items;
+        public virtual IDictionary<object, object?> Items => _connectionContext.Items;
 
         // Used by HubConnectionHandler to determine whether to set CloseMessage.AllowReconnect.
         internal bool AllowReconnect => _allowReconnect;
@@ -127,12 +127,12 @@ namespace Microsoft.AspNetCore.SignalR
         /// <summary>
         /// Gets or sets the user identifier for this connection.
         /// </summary>
-        public string UserIdentifier { get; set; }
+        public string? UserIdentifier { get; set; }
 
         /// <summary>
         /// Gets the protocol used by this connection.
         /// </summary>
-        public virtual IHubProtocol Protocol { get; set; }
+        public virtual IHubProtocol Protocol { get; set; } = default!;
 
         // Currently used only for streaming methods
         internal ConcurrentDictionary<string, CancellationTokenSource> ActiveRequestCancellationSources { get; } = new ConcurrentDictionary<string, CancellationTokenSource>(StringComparer.Ordinal);
@@ -405,7 +405,7 @@ namespace Microsoft.AspNetCore.SignalR
             ThreadPool.QueueUserWorkItem(_abortedCallback, this);
         }
 
-        internal async Task<bool> HandshakeAsync(TimeSpan timeout, IReadOnlyList<string> supportedProtocols, IHubProtocolResolver protocolResolver,
+        internal async Task<bool> HandshakeAsync(TimeSpan timeout, IReadOnlyList<string>? supportedProtocols, IHubProtocolResolver protocolResolver,
             IUserIdProvider userIdProvider, bool enableDetailedErrors)
         {
             try
@@ -455,7 +455,7 @@ namespace Microsoft.AspNetCore.SignalR
                                     consumed = segment.Start;
                                     examined = consumed;
 
-                                    Protocol = protocolResolver.GetProtocol(handshakeRequestMessage.Protocol, supportedProtocols);
+                                    Protocol = protocolResolver.GetProtocol(handshakeRequestMessage.Protocol, supportedProtocols)!;
                                     if (Protocol == null)
                                     {
                                         Log.HandshakeFailed(_logger, null);
@@ -506,7 +506,7 @@ namespace Microsoft.AspNetCore.SignalR
                                 }
                                 else if (overLength)
                                 {
-                                    Log.HandshakeSizeLimitExceeded(_logger, _maxMessageSize.Value);
+                                    Log.HandshakeSizeLimitExceeded(_logger, _maxMessageSize!.Value);
                                     await WriteHandshakeResponseAsync(new HandshakeResponseMessage("Handshake was canceled."));
                                     return false;
                                 }
@@ -619,9 +619,9 @@ namespace Microsoft.AspNetCore.SignalR
             }
         }
 
-        private static void AbortConnection(object state)
+        private static void AbortConnection(object? state)
         {
-            var connection = (HubConnectionContext)state;
+            var connection = (HubConnectionContext)state!;
 
             try
             {
@@ -684,89 +684,5 @@ namespace Microsoft.AspNetCore.SignalR
                 _streamTracker.CompleteAll(new OperationCanceledException("The underlying connection was closed."));
             }
         }
-
-        private static class Log
-        {
-            // Category: HubConnectionContext
-            private static readonly Action<ILogger, string, Exception> _handshakeComplete =
-                LoggerMessage.Define<string>(LogLevel.Debug, new EventId(1, "HandshakeComplete"), "Completed connection handshake. Using HubProtocol '{Protocol}'.");
-
-            private static readonly Action<ILogger, Exception> _handshakeCanceled =
-                LoggerMessage.Define(LogLevel.Debug, new EventId(2, "HandshakeCanceled"), "Handshake was canceled.");
-
-            private static readonly Action<ILogger, Exception> _sentPing =
-                LoggerMessage.Define(LogLevel.Trace, new EventId(3, "SentPing"), "Sent a ping message to the client.");
-
-            private static readonly Action<ILogger, Exception> _transportBufferFull =
-                LoggerMessage.Define(LogLevel.Debug, new EventId(4, "TransportBufferFull"), "Unable to send Ping message to client, the transport buffer is full.");
-
-            private static readonly Action<ILogger, Exception> _handshakeFailed =
-                LoggerMessage.Define(LogLevel.Debug, new EventId(5, "HandshakeFailed"), "Failed connection handshake.");
-
-            private static readonly Action<ILogger, Exception> _failedWritingMessage =
-                LoggerMessage.Define(LogLevel.Error, new EventId(6, "FailedWritingMessage"), "Failed writing message. Aborting connection.");
-
-            private static readonly Action<ILogger, string, int, Exception> _protocolVersionFailed =
-                LoggerMessage.Define<string, int>(LogLevel.Debug, new EventId(7, "ProtocolVersionFailed"), "Server does not support version {Version} of the {Protocol} protocol.");
-
-            private static readonly Action<ILogger, Exception> _abortFailed =
-                LoggerMessage.Define(LogLevel.Trace, new EventId(8, "AbortFailed"), "Abort callback failed.");
-
-            private static readonly Action<ILogger, int, Exception> _clientTimeout =
-                LoggerMessage.Define<int>(LogLevel.Debug, new EventId(9, "ClientTimeout"), "Client timeout ({ClientTimeout}ms) elapsed without receiving a message from the client. Closing connection.");
-
-            private static readonly Action<ILogger, long, Exception> _handshakeSizeLimitExceeded =
-                LoggerMessage.Define<long>(LogLevel.Debug, new EventId(10, "HandshakeSizeLimitExceeded"), "The maximum message size of {MaxMessageSize}B was exceeded while parsing the Handshake. The message size can be configured in AddHubOptions.");
-
-            public static void HandshakeComplete(ILogger logger, string hubProtocol)
-            {
-                _handshakeComplete(logger, hubProtocol, null);
-            }
-
-            public static void HandshakeCanceled(ILogger logger)
-            {
-                _handshakeCanceled(logger, null);
-            }
-
-            public static void SentPing(ILogger logger)
-            {
-                _sentPing(logger, null);
-            }
-
-            public static void TransportBufferFull(ILogger logger)
-            {
-                _transportBufferFull(logger, null);
-            }
-
-            public static void HandshakeFailed(ILogger logger, Exception exception)
-            {
-                _handshakeFailed(logger, exception);
-            }
-
-            public static void FailedWritingMessage(ILogger logger, Exception exception)
-            {
-                _failedWritingMessage(logger, exception);
-            }
-
-            public static void ProtocolVersionFailed(ILogger logger, string protocolName, int version)
-            {
-                _protocolVersionFailed(logger, protocolName, version, null);
-            }
-
-            public static void AbortFailed(ILogger logger, Exception exception)
-            {
-                _abortFailed(logger, exception);
-            }
-
-            public static void ClientTimeout(ILogger logger, TimeSpan timeout)
-            {
-                _clientTimeout(logger, (int)timeout.TotalMilliseconds, null);
-            }
-
-            public static void HandshakeSizeLimitExceeded(ILogger logger, long maxMessageSize)
-            {
-                _handshakeSizeLimitExceeded(logger, maxMessageSize, null);
-            }
-        }
     }
 }

src/SignalR/server/Core/src/HubConnectionContextOptions.cs

@@ -31,6 +31,6 @@ namespace Microsoft.AspNetCore.SignalR
         /// </summary>
         public long? MaximumReceiveMessageSize { get; set; }
 
-        internal ISystemClock SystemClock { get; set; }
+        internal ISystemClock SystemClock { get; set; } = default!;
     }
 }

src/SignalR/server/Core/src/HubConnectionHandler.cs

@@ -65,7 +65,7 @@ namespace Microsoft.AspNetCore.SignalR
 
             _enableDetailedErrors = false;
 
-            List<IHubFilter> hubFilters = null;
+            List<IHubFilter>? hubFilters = null;
             if (_hubOptions.UserHasSetValues)
             {
                 _maximumMessageSize = _hubOptions.MaximumReceiveMessageSize;
@@ -185,7 +185,7 @@ namespace Microsoft.AspNetCore.SignalR
             await HubOnDisconnectedAsync(connection, connection.CloseException);
         }
 
-        private async Task HubOnDisconnectedAsync(HubConnectionContext connection, Exception exception)
+        private async Task HubOnDisconnectedAsync(HubConnectionContext connection, Exception? exception)
         {
             // send close message before aborting the connection
             await SendCloseAsync(connection, exception, connection.AllowReconnect);
@@ -207,7 +207,7 @@ namespace Microsoft.AspNetCore.SignalR
             }
         }
 
-        private async Task SendCloseAsync(HubConnectionContext connection, Exception exception, bool allowReconnect)
+        private async Task SendCloseAsync(HubConnectionContext connection, Exception? exception, bool allowReconnect)
         {
             var closeMessage = CloseMessage.Empty;
 
@@ -335,22 +335,22 @@ namespace Microsoft.AspNetCore.SignalR
 
         private static class Log
         {
-            private static readonly Action<ILogger, string, Exception> _errorDispatchingHubEvent =
+            private static readonly Action<ILogger, string, Exception?> _errorDispatchingHubEvent =
                 LoggerMessage.Define<string>(LogLevel.Error, new EventId(1, "ErrorDispatchingHubEvent"), "Error when dispatching '{HubMethod}' on hub.");
 
-            private static readonly Action<ILogger, Exception> _errorProcessingRequest =
+            private static readonly Action<ILogger, Exception?> _errorProcessingRequest =
                 LoggerMessage.Define(LogLevel.Debug, new EventId(2, "ErrorProcessingRequest"), "Error when processing requests.");
 
-            private static readonly Action<ILogger, Exception> _abortFailed =
+            private static readonly Action<ILogger, Exception?> _abortFailed =
                 LoggerMessage.Define(LogLevel.Trace, new EventId(3, "AbortFailed"), "Abort callback failed.");
 
-            private static readonly Action<ILogger, Exception> _errorSendingClose =
+            private static readonly Action<ILogger, Exception?> _errorSendingClose =
                 LoggerMessage.Define(LogLevel.Debug, new EventId(4, "ErrorSendingClose"), "Error when sending Close message.");
 
-            private static readonly Action<ILogger, Exception> _connectedStarting =
+            private static readonly Action<ILogger, Exception?> _connectedStarting =
                 LoggerMessage.Define(LogLevel.Debug, new EventId(5, "ConnectedStarting"), "OnConnectedAsync started.");
 
-            private static readonly Action<ILogger, Exception> _connectedEnding =
+            private static readonly Action<ILogger, Exception?> _connectedEnding =
                 LoggerMessage.Define(LogLevel.Debug, new EventId(6, "ConnectedEnding"), "OnConnectedAsync ending.");
 
             public static void ErrorDispatchingHubEvent(ILogger logger, string hubMethod, Exception exception)

src/SignalR/server/Core/src/HubConnectionStore.cs

@@ -1,4 +1,4 @@
-// Copyright (c) .NET Foundation. All rights reserved.
+// Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System;
@@ -13,7 +13,7 @@ namespace Microsoft.AspNetCore.SignalR
         private readonly ConcurrentDictionary<string, HubConnectionContext> _connections =
             new ConcurrentDictionary<string, HubConnectionContext>(StringComparer.Ordinal);
 
-        public HubConnectionContext this[string connectionId]
+        public HubConnectionContext? this[string connectionId]
         {
             get
             {

src/SignalR/server/Core/src/HubInvocationContext.cs

@@ -14,7 +14,7 @@ namespace Microsoft.AspNetCore.SignalR
     /// </summary>
     public class HubInvocationContext
     {
-        internal ObjectMethodExecutor ObjectMethodExecutor { get; }
+        internal ObjectMethodExecutor ObjectMethodExecutor { get; } = default!;
 
         /// <summary>
         /// Instantiates a new instance of the <see cref="HubInvocationContext"/> class.
@@ -24,7 +24,7 @@ namespace Microsoft.AspNetCore.SignalR
         /// <param name="hub">The instance of the Hub.</param>
         /// <param name="hubMethod">The <see cref="MethodInfo"/> for the Hub method being invoked.</param>
         /// <param name="hubMethodArguments">The arguments provided by the client.</param>
-        public HubInvocationContext(HubCallerContext context, IServiceProvider serviceProvider, Hub hub, MethodInfo hubMethod, IReadOnlyList<object> hubMethodArguments)
+        public HubInvocationContext(HubCallerContext context, IServiceProvider serviceProvider, Hub hub, MethodInfo hubMethod, IReadOnlyList<object?> hubMethodArguments)
         {
             Hub = hub;
             ServiceProvider = serviceProvider;
@@ -40,12 +40,12 @@ namespace Microsoft.AspNetCore.SignalR
         /// <param name="hubMethodName">The name of the Hub method being invoked.</param>
         /// <param name="hubMethodArguments">The arguments provided by the client.</param>
         [Obsolete("This constructor is obsolete and will be removed in a future version. The recommended alternative is to use the other constructor.")]
-        public HubInvocationContext(HubCallerContext context, string hubMethodName, object[] hubMethodArguments)
+        public HubInvocationContext(HubCallerContext context, string hubMethodName, object?[] hubMethodArguments)
         {
             throw new NotSupportedException("This constructor no longer works. Use the other constructor.");
         }
 
-        internal HubInvocationContext(ObjectMethodExecutor objectMethodExecutor, HubCallerContext context, IServiceProvider serviceProvider, Hub hub, object[] hubMethodArguments)
+        internal HubInvocationContext(ObjectMethodExecutor objectMethodExecutor, HubCallerContext context, IServiceProvider serviceProvider, Hub hub, object?[] hubMethodArguments)
             : this(context, serviceProvider, hub, objectMethodExecutor.MethodInfo, hubMethodArguments)
         {
             ObjectMethodExecutor = objectMethodExecutor;
@@ -69,7 +69,7 @@ namespace Microsoft.AspNetCore.SignalR
         /// <summary>
         /// Gets the arguments provided by the client.
         /// </summary>
-        public IReadOnlyList<object> HubMethodArguments { get; }
+        public IReadOnlyList<object?> HubMethodArguments { get; }
 
         /// <summary>
         /// The <see cref="IServiceProvider"/> specific to the scope of this Hub method invocation.

src/SignalR/server/Core/src/HubLifetimeManager.cs

@@ -35,7 +35,7 @@ namespace Microsoft.AspNetCore.SignalR
         /// <param name="args">The invocation arguments.</param>
         /// <param name="cancellationToken">The token to monitor for cancellation requests. The default value is <see cref="CancellationToken.None" />.</param>
         /// <returns>A <see cref="Task"/> that represents the asynchronous send.</returns>
-        public abstract Task SendAllAsync(string methodName, object[] args, CancellationToken cancellationToken = default);
+        public abstract Task SendAllAsync(string methodName, object?[]? args, CancellationToken cancellationToken = default);
 
         /// <summary>
         /// Sends an invocation message to all hub connections excluding the specified connections.
@@ -45,7 +45,7 @@ namespace Microsoft.AspNetCore.SignalR
         /// <param name="excludedConnectionIds">A collection of connection IDs to exclude.</param>
         /// <param name="cancellationToken">The token to monitor for cancellation requests. The default value is <see cref="CancellationToken.None" />.</param>
         /// <returns>A <see cref="Task"/> that represents the asynchronous send.</returns>
-        public abstract Task SendAllExceptAsync(string methodName, object[] args, IReadOnlyList<string> excludedConnectionIds, CancellationToken cancellationToken = default);
+        public abstract Task SendAllExceptAsync(string methodName, object?[]? args, IReadOnlyList<string> excludedConnectionIds, CancellationToken cancellationToken = default);
 
         /// <summary>
         /// Sends an invocation message to the specified connection.
@@ -55,7 +55,7 @@ namespace Microsoft.AspNetCore.SignalR
         /// <param name="args">The invocation arguments.</param>
         /// <param name="cancellationToken">The token to monitor for cancellation requests. The default value is <see cref="CancellationToken.None" />.</param>
         /// <returns>A <see cref="Task"/> that represents the asynchronous send.</returns>
-        public abstract Task SendConnectionAsync(string connectionId, string methodName, object[] args, CancellationToken cancellationToken = default);
+        public abstract Task SendConnectionAsync(string connectionId, string methodName, object?[]? args, CancellationToken cancellationToken = default);
 
         /// <summary>
         /// Sends an invocation message to the specified connections.
@@ -65,7 +65,7 @@ namespace Microsoft.AspNetCore.SignalR
         /// <param name="args">The invocation arguments.</param>
         /// <param name="cancellationToken">The token to monitor for cancellation requests. The default value is <see cref="CancellationToken.None" />.</param>
         /// <returns>A <see cref="Task"/> that represents the asynchronous send.</returns>
-        public abstract Task SendConnectionsAsync(IReadOnlyList<string> connectionIds, string methodName, object[] args, CancellationToken cancellationToken = default);
+        public abstract Task SendConnectionsAsync(IReadOnlyList<string> connectionIds, string methodName, object?[]? args, CancellationToken cancellationToken = default);
 
         /// <summary>
         /// Sends an invocation message to the specified group.
@@ -75,7 +75,7 @@ namespace Microsoft.AspNetCore.SignalR
         /// <param name="args">The invocation arguments.</param>
         /// <param name="cancellationToken">The token to monitor for cancellation requests. The default value is <see cref="CancellationToken.None" />.</param>
         /// <returns>A <see cref="Task"/> that represents the asynchronous send.</returns>
-        public abstract Task SendGroupAsync(string groupName, string methodName, object[] args, CancellationToken cancellationToken = default);
+        public abstract Task SendGroupAsync(string groupName, string methodName, object?[]? args, CancellationToken cancellationToken = default);
 
         /// <summary>
         /// Sends an invocation message to the specified groups.
@@ -85,7 +85,7 @@ namespace Microsoft.AspNetCore.SignalR
         /// <param name="args">The invocation arguments.</param>
         /// <param name="cancellationToken">The token to monitor for cancellation requests. The default value is <see cref="CancellationToken.None" />.</param>
         /// <returns>A <see cref="Task"/> that represents the asynchronous send.</returns>
-        public abstract Task SendGroupsAsync(IReadOnlyList<string> groupNames, string methodName, object[] args, CancellationToken cancellationToken = default);
+        public abstract Task SendGroupsAsync(IReadOnlyList<string> groupNames, string methodName, object?[]? args, CancellationToken cancellationToken = default);
 
         /// <summary>
         /// Sends an invocation message to the specified group excluding the specified connections.
@@ -96,7 +96,7 @@ namespace Microsoft.AspNetCore.SignalR
         /// <param name="excludedConnectionIds">A collection of connection IDs to exclude.</param>
         /// <param name="cancellationToken">The token to monitor for cancellation requests. The default value is <see cref="CancellationToken.None" />.</param>
         /// <returns>A <see cref="Task"/> that represents the asynchronous send.</returns>
-        public abstract Task SendGroupExceptAsync(string groupName, string methodName, object[] args, IReadOnlyList<string> excludedConnectionIds, CancellationToken cancellationToken = default);
+        public abstract Task SendGroupExceptAsync(string groupName, string methodName, object?[]? args, IReadOnlyList<string> excludedConnectionIds, CancellationToken cancellationToken = default);
 
         /// <summary>
         /// Sends an invocation message to the specified user.
@@ -106,7 +106,7 @@ namespace Microsoft.AspNetCore.SignalR
         /// <param name="args">The invocation arguments.</param>
         /// <param name="cancellationToken">The token to monitor for cancellation requests. The default value is <see cref="CancellationToken.None" />.</param>
         /// <returns>A <see cref="Task"/> that represents the asynchronous send.</returns>
-        public abstract Task SendUserAsync(string userId, string methodName, object[] args, CancellationToken cancellationToken = default);
+        public abstract Task SendUserAsync(string userId, string methodName, object?[]? args, CancellationToken cancellationToken = default);
 
         /// <summary>
         /// Sends an invocation message to the specified users.
@@ -116,7 +116,7 @@ namespace Microsoft.AspNetCore.SignalR
         /// <param name="args">The invocation arguments.</param>
         /// <param name="cancellationToken">The token to monitor for cancellation requests. The default value is <see cref="CancellationToken.None" />.</param>
         /// <returns>A <see cref="Task"/> that represents the asynchronous send.</returns>
-        public abstract Task SendUsersAsync(IReadOnlyList<string> userIds, string methodName, object[] args, CancellationToken cancellationToken = default);
+        public abstract Task SendUsersAsync(IReadOnlyList<string> userIds, string methodName, object?[]? args, CancellationToken cancellationToken = default);
 
         /// <summary>
         /// Adds a connection to the specified group.

src/SignalR/server/Core/src/HubOptions.cs

@@ -34,7 +34,7 @@ namespace Microsoft.AspNetCore.SignalR
         /// <summary>
         /// Gets or sets a collection of supported hub protocol names.
         /// </summary>
-        public IList<string> SupportedProtocols { get; set; } = null;
+        public IList<string>? SupportedProtocols { get; set; }
 
         /// <summary>
         /// Gets or sets the maximum message size of a single incoming hub message. The default is 32KB.
@@ -52,6 +52,6 @@ namespace Microsoft.AspNetCore.SignalR
         /// </summary>
         public int? StreamBufferCapacity { get; set; } = null;
 
-        internal List<IHubFilter> HubFilters { get; set; } = null;
+        internal List<IHubFilter>? HubFilters { get; set; }
     }
 }

src/SignalR/server/Core/src/HubOptionsSetup`T.cs

@@ -1,6 +1,7 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
+using System;
 using System.Collections.Generic;
 using Microsoft.Extensions.Options;
 
@@ -17,7 +18,7 @@ namespace Microsoft.AspNetCore.SignalR
         public void Configure(HubOptions<THub> options)
         {
             // Do a deep copy, otherwise users modifying the HubOptions<THub> list would be changing the global options list
-            options.SupportedProtocols = new List<string>(_hubOptions.SupportedProtocols);
+            options.SupportedProtocols = new List<string>(_hubOptions.SupportedProtocols ?? Array.Empty<string>());
             options.KeepAliveInterval = _hubOptions.KeepAliveInterval;
             options.HandshakeTimeout = _hubOptions.HandshakeTimeout;
             options.ClientTimeoutInterval = _hubOptions.ClientTimeoutInterval;

src/SignalR/server/Core/src/Hub`T.cs

@@ -1,4 +1,4 @@
-// Copyright (c) .NET Foundation. All rights reserved.
+// Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using Microsoft.AspNetCore.SignalR.Internal;
@@ -11,7 +11,7 @@ namespace Microsoft.AspNetCore.SignalR
     /// <typeparam name="T">The type of client.</typeparam>
     public abstract class Hub<T> : Hub where T : class
     {
-        private IHubCallerClients<T> _clients;
+        private IHubCallerClients<T>? _clients;
 
         /// <summary>
         /// Gets or sets a <typeparamref name="T"/> that can be used to invoke methods on the clients connected to this hub.

src/SignalR/server/Core/src/IClientProxy.cs

@@ -23,6 +23,6 @@ namespace Microsoft.AspNetCore.SignalR
         /// <param name="args">A collection of arguments to pass to the client.</param>
         /// <param name="cancellationToken">The token to monitor for cancellation requests. The default value is <see cref="CancellationToken.None" />.</param>
         /// <returns>A <see cref="Task"/> that represents the asynchronous invoke.</returns>
-        Task SendCoreAsync(string method, object[] args, CancellationToken cancellationToken = default);
+        Task SendCoreAsync(string method, object?[]? args, CancellationToken cancellationToken = default);
     }
 }

src/SignalR/server/Core/src/IHubFilter.cs

@@ -1,8 +1,6 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
-#nullable enable
-
 using System;
 using System.Threading.Tasks;
 
@@ -19,7 +17,7 @@ namespace Microsoft.AspNetCore.SignalR
         /// <param name="invocationContext">The context for the method invocation that holds all the important information about the invoke.</param>
         /// <param name="next">The next filter to run, and for the final one, the Hub invocation.</param>
         /// <returns>Returns the result of the Hub method invoke.</returns>
-        ValueTask<object> InvokeMethodAsync(HubInvocationContext invocationContext, Func<HubInvocationContext, ValueTask<object>> next) => next(invocationContext);
+        ValueTask<object?> InvokeMethodAsync(HubInvocationContext invocationContext, Func<HubInvocationContext, ValueTask<object?>> next) => next(invocationContext);
 
         /// <summary>
         /// Allows handling of the <see cref="Hub.OnConnectedAsync"/> method.
@@ -36,6 +34,6 @@ namespace Microsoft.AspNetCore.SignalR
         /// <param name="exception">The exception, if any, for the connection closing.</param>
         /// <param name="next">The next filter to run, and for the final one, the Hub invocation.</param>
         /// <returns></returns>
-        Task OnDisconnectedAsync(HubLifetimeContext context, Exception exception, Func<HubLifetimeContext, Exception, Task> next) => next(context, exception);
+        Task OnDisconnectedAsync(HubLifetimeContext context, Exception? exception, Func<HubLifetimeContext, Exception?, Task> next) => next(context, exception);
     }
 }

src/SignalR/server/Core/src/IHubProtocolResolver.cs

@@ -22,6 +22,6 @@ namespace Microsoft.AspNetCore.SignalR
         /// <param name="protocolName">The protocol name.</param>
         /// <param name="supportedProtocols">A collection of supported protocols.</param>
         /// <returns>A matching <see cref="IHubProtocol"/> or <c>null</c> if no matching protocol was found.</returns>
-        IHubProtocol GetProtocol(string protocolName, IReadOnlyList<string> supportedProtocols);
+        IHubProtocol? GetProtocol(string protocolName, IReadOnlyList<string>? supportedProtocols);
     }
 }

src/SignalR/server/Core/src/IUserIdProvider.cs

@@ -1,4 +1,4 @@
-// Copyright (c) .NET Foundation. All rights reserved.
+// Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 namespace Microsoft.AspNetCore.SignalR
@@ -14,6 +14,6 @@ namespace Microsoft.AspNetCore.SignalR
         /// </summary>
         /// <param name="connection">The connection to get the user ID for.</param>
         /// <returns>The user ID for the specified connection.</returns>
-        string GetUserId(HubConnectionContext connection);
+        string? GetUserId(HubConnectionContext connection);
     }
-}
+}

src/SignalR/server/Core/src/Internal/DefaultHubCallerContext.cs

@@ -24,13 +24,13 @@ namespace Microsoft.AspNetCore.SignalR.Internal
         public override string ConnectionId => _connection.ConnectionId;
 
         /// <inheritdoc />
-        public override string UserIdentifier => _connection.UserIdentifier;
+        public override string? UserIdentifier => _connection.UserIdentifier;
 
         /// <inheritdoc />
-        public override ClaimsPrincipal User => _connection.User;
+        public override ClaimsPrincipal? User => _connection.User;
 
         /// <inheritdoc />
-        public override IDictionary<object, object> Items => _connection.Items;
+        public override IDictionary<object, object?> Items => _connection.Items;
 
         /// <inheritdoc />
         public override IFeatureCollection Features => _connection.Features;

src/SignalR/server/Core/src/Internal/DefaultHubDispatcher.Log.cs

@@ -1,6 +1,8 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
+#nullable disable
+
 using System;
 using Microsoft.AspNetCore.SignalR.Protocol;
 using Microsoft.Extensions.Internal;

src/SignalR/server/Core/src/Internal/DefaultHubDispatcher.cs

@@ -1,6 +1,8 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
+#nullable disable
+
 using System;
 using System.Collections.Generic;
 using System.Diagnostics;

src/SignalR/server/Core/src/Internal/DefaultHubProtocolResolver.cs

@@ -31,7 +31,7 @@ namespace Microsoft.AspNetCore.SignalR.Internal
             _hubProtocols = _availableProtocols.Values.ToList();
         }
 
-        public virtual IHubProtocol GetProtocol(string protocolName, IReadOnlyList<string> supportedProtocols)
+        public virtual IHubProtocol? GetProtocol(string protocolName, IReadOnlyList<string>? supportedProtocols)
         {
             protocolName = protocolName ?? throw new ArgumentNullException(nameof(protocolName));
 
@@ -49,10 +49,10 @@ namespace Microsoft.AspNetCore.SignalR.Internal
         private static class Log
         {
             // Category: DefaultHubProtocolResolver
-            private static readonly Action<ILogger, string, Type, Exception> _registeredSignalRProtocol =
+            private static readonly Action<ILogger, string, Type, Exception?> _registeredSignalRProtocol =
                 LoggerMessage.Define<string, Type>(LogLevel.Debug, new EventId(1, "RegisteredSignalRProtocol"), "Registered SignalR Protocol: {ProtocolName}, implemented by {ImplementationType}.");
 
-            private static readonly Action<ILogger, string, Exception> _foundImplementationForProtocol =
+            private static readonly Action<ILogger, string, Exception?> _foundImplementationForProtocol =
                 LoggerMessage.Define<string>(LogLevel.Debug, new EventId(2, "FoundImplementationForProtocol"), "Found protocol implementation for requested protocol: {ProtocolName}.");
 
             public static void RegisteredSignalRProtocol(ILogger logger, string protocolName, Type implementationType)

src/SignalR/server/Core/src/Internal/DynamicClientProxy.cs

@@ -1,4 +1,4 @@
-// Copyright (c) .NET Foundation. All rights reserved.
+// Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System.Dynamic;
@@ -14,7 +14,7 @@ namespace Microsoft.AspNetCore.SignalR.Internal
             _clientProxy = clientProxy;
         }
 
-        public override bool TryInvokeMember(InvokeMemberBinder binder, object[] args, out object result)
+        public override bool TryInvokeMember(InvokeMemberBinder binder, object?[]? args, out object? result)
         {
             result = _clientProxy.SendCoreAsync(binder.Name, args);
             return true;

src/SignalR/server/Core/src/Internal/HubDispatcher.cs

@@ -11,7 +11,7 @@ namespace Microsoft.AspNetCore.SignalR.Internal
     internal abstract class HubDispatcher<THub> where THub : Hub
     {
         public abstract Task OnConnectedAsync(HubConnectionContext connection);
-        public abstract Task OnDisconnectedAsync(HubConnectionContext connection, Exception exception);
+        public abstract Task OnDisconnectedAsync(HubConnectionContext connection, Exception? exception);
         public abstract Task DispatchMessageAsync(HubConnectionContext connection, HubMessage hubMessage);
         public abstract IReadOnlyList<Type> GetParameterTypes(string name);
     }

src/SignalR/server/Core/src/Internal/HubFilterFactory.cs

@@ -1,8 +1,6 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
-#nullable enable
-
 using System;
 using System.Diagnostics.CodeAnalysis;
 using System.Threading.Tasks;
@@ -23,7 +21,7 @@ namespace Microsoft.AspNetCore.SignalR.Internal
             _filterType = filterType;
         }
 
-        public async ValueTask<object> InvokeMethodAsync(HubInvocationContext invocationContext, Func<HubInvocationContext, ValueTask<object>> next)
+        public async ValueTask<object?> InvokeMethodAsync(HubInvocationContext invocationContext, Func<HubInvocationContext, ValueTask<object?>> next)
         {
             var (filter, owned) = GetFilter(invocationContext.ServiceProvider);
 
@@ -57,7 +55,7 @@ namespace Microsoft.AspNetCore.SignalR.Internal
             }
         }
 
-        public async Task OnDisconnectedAsync(HubLifetimeContext context, Exception exception, Func<HubLifetimeContext, Exception, Task> next)
+        public async Task OnDisconnectedAsync(HubLifetimeContext context, Exception? exception, Func<HubLifetimeContext, Exception?, Task> next)
         {
             var (filter, owned) = GetFilter(context.ServiceProvider);
 

src/SignalR/server/Core/src/Internal/HubGroupList.cs

@@ -1,4 +1,4 @@
-// Copyright (c) .NET Foundation. All rights reserved.
+// Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System;
@@ -16,7 +16,7 @@ namespace Microsoft.AspNetCore.SignalR.Internal
 
         private static readonly GroupConnectionList EmptyGroupConnectionList = new GroupConnectionList();
 
-        public ConcurrentDictionary<string, HubConnectionContext> this[string groupName]
+        public ConcurrentDictionary<string, HubConnectionContext>? this[string groupName]
         {
             get
             {
@@ -86,7 +86,7 @@ namespace Microsoft.AspNetCore.SignalR.Internal
 
     internal class GroupConnectionList : ConcurrentDictionary<string, HubConnectionContext>
     {
-        public override bool Equals(object obj)
+        public override bool Equals(object? obj)
         {
             if (obj is ConcurrentDictionary<string, HubConnectionContext> list)
             {
@@ -101,4 +101,4 @@ namespace Microsoft.AspNetCore.SignalR.Internal
             return base.GetHashCode();
         }
     }
-}
+}

src/SignalR/server/Core/src/Internal/HubMethodDescriptor.cs

@@ -1,6 +1,8 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
+#nullable disable
+
 using System;
 using System.Collections.Generic;
 using System.Linq;

src/SignalR/server/Core/src/Internal/HubReflectionHelper.cs

@@ -32,7 +32,7 @@ namespace Microsoft.AspNetCore.SignalR.Internal
 
         private static bool IsHubMethod(MethodInfo methodInfo)
         {
-            var baseDefinition = methodInfo.GetBaseDefinition().DeclaringType;
+            var baseDefinition = methodInfo.GetBaseDefinition().DeclaringType!;
             if (typeof(object) == baseDefinition || methodInfo.IsSpecialName)
             {
                 return false;

src/SignalR/server/Core/src/Internal/Proxies.cs

@@ -18,7 +18,7 @@ namespace Microsoft.AspNetCore.SignalR.Internal
             _userId = userId;
         }
 
-        public Task SendCoreAsync(string method, object[] args, CancellationToken cancellationToken = default)
+        public Task SendCoreAsync(string method, object?[]? args, CancellationToken cancellationToken = default)
         {
             return _lifetimeManager.SendUserAsync(_userId, method, args, cancellationToken);
         }
@@ -35,7 +35,7 @@ namespace Microsoft.AspNetCore.SignalR.Internal
             _userIds = userIds;
         }
 
-        public Task SendCoreAsync(string method, object[] args, CancellationToken cancellationToken = default)
+        public Task SendCoreAsync(string method, object?[]? args, CancellationToken cancellationToken = default)
         {
             return _lifetimeManager.SendUsersAsync(_userIds, method, args, cancellationToken);
         }
@@ -52,7 +52,7 @@ namespace Microsoft.AspNetCore.SignalR.Internal
             _groupName = groupName;
         }
 
-        public Task SendCoreAsync(string method, object[] args, CancellationToken cancellationToken = default)
+        public Task SendCoreAsync(string method, object?[]? args, CancellationToken cancellationToken = default)
         {
             return _lifetimeManager.SendGroupAsync(_groupName, method, args, cancellationToken);
         }
@@ -69,7 +69,7 @@ namespace Microsoft.AspNetCore.SignalR.Internal
             _groupNames = groupNames;
         }
 
-        public Task SendCoreAsync(string method, object[] args, CancellationToken cancellationToken = default)
+        public Task SendCoreAsync(string method, object?[]? args, CancellationToken cancellationToken = default)
         {
             return _lifetimeManager.SendGroupsAsync(_groupNames, method, args, cancellationToken);
         }
@@ -88,7 +88,7 @@ namespace Microsoft.AspNetCore.SignalR.Internal
             _excludedConnectionIds = excludedConnectionIds;
         }
 
-        public Task SendCoreAsync(string method, object[] args, CancellationToken cancellationToken = default)
+        public Task SendCoreAsync(string method, object?[]? args, CancellationToken cancellationToken = default)
         {
             return _lifetimeManager.SendGroupExceptAsync(_groupName, method, args, _excludedConnectionIds, cancellationToken);
         }
@@ -103,7 +103,7 @@ namespace Microsoft.AspNetCore.SignalR.Internal
             _lifetimeManager = lifetimeManager;
         }
 
-        public Task SendCoreAsync(string method, object[] args, CancellationToken cancellationToken = default)
+        public Task SendCoreAsync(string method, object?[]? args, CancellationToken cancellationToken = default)
         {
             return _lifetimeManager.SendAllAsync(method, args, cancellationToken);
         }
@@ -120,7 +120,7 @@ namespace Microsoft.AspNetCore.SignalR.Internal
             _excludedConnectionIds = excludedConnectionIds;
         }
 
-        public Task SendCoreAsync(string method, object[] args, CancellationToken cancellationToken = default)
+        public Task SendCoreAsync(string method, object?[]? args, CancellationToken cancellationToken = default)
         {
             return _lifetimeManager.SendAllExceptAsync(method, args, _excludedConnectionIds, cancellationToken);
         }
@@ -137,7 +137,7 @@ namespace Microsoft.AspNetCore.SignalR.Internal
             _connectionId = connectionId;
         }
 
-        public Task SendCoreAsync(string method, object[] args, CancellationToken cancellationToken = default)
+        public Task SendCoreAsync(string method, object?[]? args, CancellationToken cancellationToken = default)
         {
             return _lifetimeManager.SendConnectionAsync(_connectionId, method, args, cancellationToken);
         }
@@ -154,7 +154,7 @@ namespace Microsoft.AspNetCore.SignalR.Internal
             _connectionIds = connectionIds;
         }
 
-        public Task SendCoreAsync(string method, object[] args, CancellationToken cancellationToken = default)
+        public Task SendCoreAsync(string method, object?[]? args, CancellationToken cancellationToken = default)
         {
             return _lifetimeManager.SendConnectionsAsync(_connectionIds, method, args, cancellationToken);
         }

src/SignalR/server/Core/src/Internal/TypedClientBuilder.cs

@@ -1,6 +1,8 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
+#nullable disable
+
 using System;
 using System.Collections.Generic;
 using System.Linq;

src/SignalR/server/Core/src/Microsoft.AspNetCore.SignalR.Core.csproj

@@ -6,6 +6,7 @@
     <IsAspNetCoreApp>true</IsAspNetCoreApp>
     <RootNamespace>Microsoft.AspNetCore.SignalR</RootNamespace>
     <IsPackable>false</IsPackable>
+    <Nullable>enable</Nullable>
   </PropertyGroup>
 
   <ItemGroup>

src/SignalR/server/Core/src/SerializedHubMessage.cs

@@ -14,13 +14,13 @@ namespace Microsoft.AspNetCore.SignalR
     {
         private SerializedMessage _cachedItem1;
         private SerializedMessage _cachedItem2;
-        private List<SerializedMessage> _cachedItems;
+        private List<SerializedMessage>? _cachedItems;
         private readonly object _lock = new object();
 
         /// <summary>
         /// Gets the hub message for the serialization cache.
         /// </summary>
-        public HubMessage Message { get; }
+        public HubMessage? Message { get; }
 
         /// <summary>
         /// Initializes a new instance of the <see cref="SerializedHubMessage"/> class.

src/SignalR/server/Core/src/StreamTracker.cs

@@ -1,6 +1,8 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
+#nullable disable
+
 using System;
 using System.Collections.Concurrent;
 using System.Collections.Generic;