Turn on nullability for Routing (#24238)

* Turn on nullability for Routing

We previously only had annotations enabled which resulted in incorrect nullability. This change enables
nullability.

Fixes https://github.com/dotnet/aspnetcore/issues/24042

src/Http/Http.Abstractions/src/Routing/Endpoint.cs

@@ -20,8 +20,8 @@ namespace Microsoft.AspNetCore.Http
         /// </param>
         public Endpoint(
             RequestDelegate requestDelegate,
-            EndpointMetadataCollection metadata,
+            EndpointMetadataCollection? metadata,
-            string displayName)
+            string? displayName)
         {
             // All are allowed to be null
             RequestDelegate = requestDelegate;
@@ -32,7 +32,7 @@ namespace Microsoft.AspNetCore.Http
         /// <summary>
         /// Gets the informational display name of this endpoint.
         /// </summary>
-        public string DisplayName { get; }
+        public string? DisplayName { get; }
 
         /// <summary>
         /// Gets the collection of metadata associated with this endpoint.

src/Http/Routing.Abstractions/src/IRouteConstraint.cs

@@ -25,7 +25,7 @@ namespace Microsoft.AspNetCore.Routing
         /// <returns><c>true</c> if the URL parameter contains a valid value; otherwise, <c>false</c>.</returns>
         bool Match(
             HttpContext? httpContext,
-            IRouter route,
+            IRouter? route,
             string routeKey,
             RouteValueDictionary values,
             RouteDirection routeDirection);

src/Http/Routing/src/ArrayBuilder.cs

@@ -6,6 +6,7 @@
 // 
 // See https://github.com/dotnet/corefx/blob/143df51926f2ad397fef9c9ca7ede88e2721e801/src/Common/src/System/Collections/Generic/ArrayBuilder.cs 
 
+#nullable disable
 
 using System;
 using System.Diagnostics;

src/Http/Routing/src/Builder/EndpointRoutingApplicationBuilderExtensions.cs

@@ -128,7 +128,7 @@ namespace Microsoft.AspNetCore.Builder
             }
 
             // If someone messes with this, just let it crash.
-            endpointRouteBuilder = (DefaultEndpointRouteBuilder)obj;
+            endpointRouteBuilder = (DefaultEndpointRouteBuilder)obj!;
 
             // This check handles the case where Map or something else that forks the pipeline is called between the two
             // routing middleware.

src/Http/Routing/src/CompositeEndpointDataSource.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;
@@ -6,6 +6,7 @@ using System.Collections.Generic;
 using System.Collections.ObjectModel;
 using System.Collections.Specialized;
 using System.Diagnostics;
+using System.Diagnostics.CodeAnalysis;
 using System.Linq;
 using System.Text;
 using System.Threading;
@@ -21,8 +22,8 @@ namespace Microsoft.AspNetCore.Routing
     public sealed class CompositeEndpointDataSource : EndpointDataSource
     {
         private readonly object _lock;
-        private readonly ICollection<EndpointDataSource> _dataSources;
+        private readonly ICollection<EndpointDataSource> _dataSources = default!;
-        private IReadOnlyList<Endpoint> _endpoints;
+        private IReadOnlyList<Endpoint> _endpoints = default!;
         private IChangeToken _consumerChangeToken;
         private CancellationTokenSource _cts;
 
@@ -49,7 +50,7 @@ namespace Microsoft.AspNetCore.Routing
             }
         }
 
-        private void OnDataSourcesChanged(object sender, NotifyCollectionChangedEventArgs e)
+        private void OnDataSourcesChanged(object? sender, NotifyCollectionChangedEventArgs e)
         {
             lock (_lock)
             {
@@ -140,6 +141,7 @@ namespace Microsoft.AspNetCore.Routing
             }
         }
 
+        [MemberNotNull(nameof(_cts), nameof(_consumerChangeToken))]
         private void CreateChangeToken()
         {
             _cts = new CancellationTokenSource();
@@ -198,7 +200,7 @@ namespace Microsoft.AspNetCore.Routing
                 }
                 return sb.ToString();
 
-                IEnumerable<string> FormatValues(IEnumerable<KeyValuePair<string, object>> values)
+                IEnumerable<string> FormatValues(IEnumerable<KeyValuePair<string, object?>> values)
                 {
                     return values.Select(
                         kvp =>

src/Http/Routing/src/Constraints/BoolRouteConstraint.cs

@@ -14,8 +14,8 @@ namespace Microsoft.AspNetCore.Routing.Constraints
     {
         /// <inheritdoc />
         public bool Match(
-            HttpContext httpContext,
+            HttpContext? httpContext,
-            IRouter route,
+            IRouter? route,
             string routeKey,
             RouteValueDictionary values,
             RouteDirection routeDirection)

src/Http/Routing/src/Constraints/CompositeRouteConstraint.cs

@@ -33,8 +33,8 @@ namespace Microsoft.AspNetCore.Routing.Constraints
 
         /// <inheritdoc />
         public bool Match(
-            HttpContext httpContext,
+            HttpContext? httpContext,
-            IRouter route,
+            IRouter? route,
             string routeKey,
             RouteValueDictionary values,
             RouteDirection routeDirection)

src/Http/Routing/src/Constraints/DateTimeRouteConstraint.cs

@@ -20,8 +20,8 @@ namespace Microsoft.AspNetCore.Routing.Constraints
     {
         /// <inheritdoc />
         public bool Match(
-            HttpContext httpContext,
+            HttpContext? httpContext,
-            IRouter route,
+            IRouter? route,
             string routeKey,
             RouteValueDictionary values,
             RouteDirection routeDirection)

src/Http/Routing/src/Constraints/DecimalRouteConstraint.cs

@@ -14,8 +14,8 @@ namespace Microsoft.AspNetCore.Routing.Constraints
     {
         /// <inheritdoc />
         public bool Match(
-            HttpContext httpContext,
+            HttpContext? httpContext,
-            IRouter route,
+            IRouter? route,
             string routeKey,
             RouteValueDictionary values,
             RouteDirection routeDirection)

src/Http/Routing/src/Constraints/DoubleRouteConstraint.cs

@@ -14,8 +14,8 @@ namespace Microsoft.AspNetCore.Routing.Constraints
     {
         /// <inheritdoc />
         public bool Match(
-            HttpContext httpContext,
+            HttpContext? httpContext,
-            IRouter route,
+            IRouter? route,
             string routeKey,
             RouteValueDictionary values,
             RouteDirection routeDirection)

src/Http/Routing/src/Constraints/FileNameRouteConstraint.cs

@@ -85,8 +85,8 @@ namespace Microsoft.AspNetCore.Routing.Constraints
     {
         /// <inheritdoc />
         public bool Match(
-            HttpContext httpContext,
+            HttpContext? httpContext,
-            IRouter route,
+            IRouter? route,
             string routeKey,
             RouteValueDictionary values,
             RouteDirection routeDirection)

src/Http/Routing/src/Constraints/FloatRouteConstraint.cs

@@ -14,8 +14,8 @@ namespace Microsoft.AspNetCore.Routing.Constraints
     {
         /// <inheritdoc />
         public bool Match(
-            HttpContext httpContext,
+            HttpContext? httpContext,
-            IRouter route,
+            IRouter? route,
             string routeKey,
             RouteValueDictionary values,
             RouteDirection routeDirection)

src/Http/Routing/src/Constraints/GuidRouteConstraint.cs

@@ -16,8 +16,8 @@ namespace Microsoft.AspNetCore.Routing.Constraints
     {
         /// <inheritdoc />
         public bool Match(
-            HttpContext httpContext,
+            HttpContext? httpContext,
-            IRouter route,
+            IRouter? route,
             string routeKey,
             RouteValueDictionary values,
             RouteDirection routeDirection)

src/Http/Routing/src/Constraints/HttpMethodRouteConstraint.cs

@@ -35,8 +35,8 @@ namespace Microsoft.AspNetCore.Routing.Constraints
 
         /// <inheritdoc />
         public virtual bool Match(
-            HttpContext httpContext,
+            HttpContext? httpContext,
-            IRouter route,
+            IRouter? route,
             string routeKey,
             RouteValueDictionary values,
             RouteDirection routeDirection)

src/Http/Routing/src/Constraints/IntRouteConstraint.cs

@@ -14,8 +14,8 @@ namespace Microsoft.AspNetCore.Routing.Constraints
     {
         /// <inheritdoc />
         public bool Match(
-            HttpContext httpContext,
+            HttpContext? httpContext,
-            IRouter route,
+            IRouter? route,
             string routeKey,
             RouteValueDictionary values,
             RouteDirection routeDirection)

src/Http/Routing/src/Constraints/LengthRouteConstraint.cs

@@ -71,8 +71,8 @@ namespace Microsoft.AspNetCore.Routing.Constraints
 
         /// <inheritdoc />
         public bool Match(
-            HttpContext httpContext,
+            HttpContext? httpContext,
-            IRouter route,
+            IRouter? route,
             string routeKey,
             RouteValueDictionary values,
             RouteDirection routeDirection)
@@ -89,7 +89,7 @@ namespace Microsoft.AspNetCore.Routing.Constraints
 
             if (values.TryGetValue(routeKey, out var value) && value != null)
             {
-                var valueString = Convert.ToString(value, CultureInfo.InvariantCulture);
+                var valueString = Convert.ToString(value, CultureInfo.InvariantCulture)!;
                 var length = valueString.Length;
                 return length >= MinLength && length <= MaxLength;
             }

src/Http/Routing/src/Constraints/LongRouteConstraint.cs

@@ -14,8 +14,8 @@ namespace Microsoft.AspNetCore.Routing.Constraints
     {
         /// <inheritdoc />
         public bool Match(
-            HttpContext httpContext,
+            HttpContext? httpContext,
-            IRouter route,
+            IRouter? route,
             string routeKey,
             RouteValueDictionary values,
             RouteDirection routeDirection)

src/Http/Routing/src/Constraints/MaxLengthRouteConstraint.cs

@@ -34,8 +34,8 @@ namespace Microsoft.AspNetCore.Routing.Constraints
 
         /// <inheritdoc />
         public bool Match(
-            HttpContext httpContext,
+            HttpContext? httpContext,
-            IRouter route,
+            IRouter? route,
             string routeKey,
             RouteValueDictionary values,
             RouteDirection routeDirection)
@@ -52,7 +52,7 @@ namespace Microsoft.AspNetCore.Routing.Constraints
 
             if (values.TryGetValue(routeKey, out var value) && value != null)
             {
-                var valueString = Convert.ToString(value, CultureInfo.InvariantCulture);
+                var valueString = Convert.ToString(value, CultureInfo.InvariantCulture)!;
                 return valueString.Length <= MaxLength;
             }
 

src/Http/Routing/src/Constraints/MaxRouteConstraint.cs

@@ -28,8 +28,8 @@ namespace Microsoft.AspNetCore.Routing.Constraints
 
         /// <inheritdoc />
         public bool Match(
-            HttpContext httpContext,
+            HttpContext? httpContext,
-            IRouter route,
+            IRouter? route,
             string routeKey,
             RouteValueDictionary values,
             RouteDirection routeDirection)

src/Http/Routing/src/Constraints/MinLengthRouteConstraint.cs

@@ -34,8 +34,8 @@ namespace Microsoft.AspNetCore.Routing.Constraints
 
         /// <inheritdoc />
         public bool Match(
-            HttpContext httpContext,
+            HttpContext? httpContext,
-            IRouter route,
+            IRouter? route,
             string routeKey,
             RouteValueDictionary values,
             RouteDirection routeDirection)
@@ -52,7 +52,7 @@ namespace Microsoft.AspNetCore.Routing.Constraints
 
             if (values.TryGetValue(routeKey, out var value) && value != null)
             {
-                var valueString = Convert.ToString(value, CultureInfo.InvariantCulture);
+                var valueString = Convert.ToString(value, CultureInfo.InvariantCulture)!;
                 return valueString.Length >= MinLength;
             }
 

src/Http/Routing/src/Constraints/MinRouteConstraint.cs

@@ -28,8 +28,8 @@ namespace Microsoft.AspNetCore.Routing.Constraints
 
         /// <inheritdoc />
         public bool Match(
-            HttpContext httpContext,
+            HttpContext? httpContext,
-            IRouter route,
+            IRouter? route,
             string routeKey,
             RouteValueDictionary values,
             RouteDirection routeDirection)

src/Http/Routing/src/Constraints/NonFileNameRouteConstraint.cs

@@ -81,8 +81,8 @@ namespace Microsoft.AspNetCore.Routing.Constraints
     {
         /// <inheritdoc />
         public bool Match(
-            HttpContext httpContext,
+            HttpContext? httpContext,
-            IRouter route,
+            IRouter? route,
             string routeKey,
             RouteValueDictionary values,
             RouteDirection routeDirection)

src/Http/Routing/src/Constraints/NullRouteConstraint.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.Http;
@@ -13,7 +13,7 @@ namespace Microsoft.AspNetCore.Routing.Constraints
         {
         }
 
-        public bool Match(HttpContext httpContext, IRouter route, string routeKey, RouteValueDictionary values, RouteDirection routeDirection)
+        public bool Match(HttpContext? httpContext, IRouter? route, string routeKey, RouteValueDictionary values, RouteDirection routeDirection)
         {
             return true;
         }

src/Http/Routing/src/Constraints/OptionalRouteConstraint.cs

@@ -24,8 +24,8 @@ namespace Microsoft.AspNetCore.Routing.Constraints
         public IRouteConstraint InnerConstraint { get; }
 
         public bool Match(
-            HttpContext httpContext,
+            HttpContext? httpContext,
-            IRouter route,
+            IRouter? route,
             string routeKey,
             RouteValueDictionary values,
             RouteDirection routeDirection)

src/Http/Routing/src/Constraints/RangeRouteConstraint.cs

@@ -42,8 +42,8 @@ namespace Microsoft.AspNetCore.Routing.Constraints
 
         /// <inheritdoc />
         public bool Match(
-            HttpContext httpContext,
+            HttpContext? httpContext,
-            IRouter route,
+            IRouter? route,
             string routeKey,
             RouteValueDictionary values,
             RouteDirection routeDirection)

src/Http/Routing/src/Constraints/RegexRouteConstraint.cs

@@ -38,8 +38,8 @@ namespace Microsoft.AspNetCore.Routing.Constraints
         public Regex Constraint { get; private set; }
 
         public bool Match(
-            HttpContext httpContext,
+            HttpContext? httpContext,
-            IRouter route,
+            IRouter? route,
             string routeKey,
             RouteValueDictionary values,
             RouteDirection routeDirection)
@@ -57,7 +57,7 @@ namespace Microsoft.AspNetCore.Routing.Constraints
             if (values.TryGetValue(routeKey, out var routeValue)
                 && routeValue != null)
             {
-                var parameterValueString = Convert.ToString(routeValue, CultureInfo.InvariantCulture);
+                var parameterValueString = Convert.ToString(routeValue, CultureInfo.InvariantCulture)!;
 
                 return Constraint.IsMatch(parameterValueString);
             }

src/Http/Routing/src/Constraints/RequiredRouteConstraint.cs

@@ -18,8 +18,8 @@ namespace Microsoft.AspNetCore.Routing.Constraints
     {
         /// <inheritdoc />
         public bool Match(
-            HttpContext httpContext,
+            HttpContext? httpContext,
-            IRouter route,
+            IRouter? route,
             string routeKey,
             RouteValueDictionary values,
             RouteDirection routeDirection)

src/Http/Routing/src/Constraints/StringRouteConstraint.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;
@@ -29,7 +29,7 @@ namespace Microsoft.AspNetCore.Routing.Constraints
         }
 
         /// <inheritdoc />
-        public bool Match(HttpContext httpContext, IRouter route, string routeKey, RouteValueDictionary values, RouteDirection routeDirection)
+        public bool Match(HttpContext? httpContext, IRouter? route, string routeKey, RouteValueDictionary values, RouteDirection routeDirection)
         {
             if (routeKey == null)
             {
@@ -44,7 +44,7 @@ namespace Microsoft.AspNetCore.Routing.Constraints
             if (values.TryGetValue(routeKey, out var routeValue)
                 && routeValue != null)
             {
-                var parameterValueString = Convert.ToString(routeValue, CultureInfo.InvariantCulture);
+                var parameterValueString = Convert.ToString(routeValue, CultureInfo.InvariantCulture)!;
 
                 return parameterValueString.Equals(_value, StringComparison.OrdinalIgnoreCase);
             }

src/Http/Routing/src/DataSourceDependentCache.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.Threading;

src/Http/Routing/src/DecisionTree/DecisionCriterion.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;
 
 namespace Microsoft.AspNetCore.Routing.DecisionTree

src/Http/Routing/src/DecisionTree/DecisionTreeNode.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;
 
 namespace Microsoft.AspNetCore.Routing.DecisionTree

src/Http/Routing/src/DecisionTree/ItemDescriptor.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;
 
 namespace Microsoft.AspNetCore.Routing.DecisionTree

src/Http/Routing/src/DefaultLinkGenerator.cs

@@ -325,7 +325,7 @@ namespace Microsoft.AspNetCore.Routing
         }
 
         // Also called from DefaultLinkGenerationTemplate
-        public static RouteValueDictionary? GetAmbientValues(HttpContext httpContext)
+        public static RouteValueDictionary? GetAmbientValues(HttpContext? httpContext)
         {
             return httpContext?.Features.Get<IRouteValuesFeature>()?.RouteValues;
         }

src/Http/Routing/src/DefaultLinkParser.cs

@@ -4,6 +4,7 @@
 using System;
 using System.Collections.Concurrent;
 using System.Collections.Generic;
+using System.Diagnostics.CodeAnalysis;
 using System.Linq;
 using Microsoft.AspNetCore.Http;
 using Microsoft.Extensions.DependencyInjection;
@@ -46,7 +47,7 @@ namespace Microsoft.AspNetCore.Routing
             _createMatcher = CreateRoutePatternMatcher;
         }
 
-        public override RouteValueDictionary ParsePathByAddress<TAddress>(TAddress address, PathString path)
+        public override RouteValueDictionary? ParsePathByAddress<TAddress>(TAddress address, PathString path)
         {
             var endpoints = GetEndpoints(address);
             if (endpoints.Count == 0)
@@ -117,7 +118,7 @@ namespace Microsoft.AspNetCore.Routing
         internal MatcherState GetMatcherState(RouteEndpoint endpoint) => _matcherCache.EnsureInitialized().GetOrAdd(endpoint, _createMatcher);
 
         // Internal for testing
-        internal bool TryParse(RouteEndpoint endpoint, PathString path, out RouteValueDictionary values)
+        internal bool TryParse(RouteEndpoint endpoint, PathString path, [NotNullWhen(true)] out RouteValueDictionary? values)
         {
             var (matcher, constraints) = GetMatcherState(endpoint);
 
@@ -168,6 +169,7 @@ namespace Microsoft.AspNetCore.Routing
             }
         }
 
+#nullable disable
         private static class Log
         {
             public static class EventIds

src/Http/Routing/src/DefaultParameterPolicyFactory.cs

@@ -21,7 +21,7 @@ namespace Microsoft.AspNetCore.Routing
             _serviceProvider = serviceProvider;
         }
 
-        public override IParameterPolicy Create(RoutePatternParameterPart parameter, IParameterPolicy parameterPolicy)
+        public override IParameterPolicy Create(RoutePatternParameterPart? parameter, IParameterPolicy parameterPolicy)
         {
             if (parameterPolicy == null)
             {
@@ -36,7 +36,7 @@ namespace Microsoft.AspNetCore.Routing
             return parameterPolicy;
         }
 
-        public override IParameterPolicy Create(RoutePatternParameterPart parameter, string inlineText)
+        public override IParameterPolicy Create(RoutePatternParameterPart? parameter, string inlineText)
         {
             if (inlineText == null)
             {

src/Http/Routing/src/EndpointMiddleware.cs

@@ -101,6 +101,7 @@ namespace Microsoft.AspNetCore.Routing
                 "Configure your application startup by adding app.UseCors() inside the call to Configure(..) in the application startup code. The call to app.UseCors() must appear between app.UseRouting() and app.UseEndpoints(...).");
         }
 
+#nullable disable
         private static class Log
         {
             private static readonly Action<ILogger, string, Exception> _executingEndpoint = LoggerMessage.Define<string>(

src/Http/Routing/src/EndpointNameAddressScheme.cs

@@ -92,7 +92,7 @@ namespace Microsoft.AspNetCore.Routing
 
             throw new InvalidOperationException(builder.ToString());
 
-            string GetEndpointName(Endpoint endpoint)
+            string? GetEndpointName(Endpoint endpoint)
             {
                 if (endpoint.Metadata.GetMetadata<ISuppressLinkGenerationMetadata>()?.SuppressLinkGeneration == true)
                 {

src/Http/Routing/src/EndpointRoutingMiddleware.cs

@@ -22,7 +22,7 @@ namespace Microsoft.AspNetCore.Routing
         private readonly DiagnosticListener _diagnosticListener;
         private readonly RequestDelegate _next;
 
-        private Task<Matcher> _initializationTask;
+        private Task<Matcher>? _initializationTask;
 
         public EndpointRoutingMiddleware(
             MatcherFactory matcherFactory,
@@ -165,6 +165,7 @@ namespace Microsoft.AspNetCore.Routing
             }
         }
 
+#nullable disable
         private static class Log
         {
             private static readonly Action<ILogger, string, Exception> _matchSuccess = LoggerMessage.Define<string>(

src/Http/Routing/src/InlineRouteParameterParser.cs

@@ -75,7 +75,7 @@ namespace Microsoft.AspNetCore.Routing
             var parseResults = ParseConstraints(routeParameter, currentIndex, endIndex);
             currentIndex = parseResults.CurrentIndex;
 
-            string defaultValue = null;
+            string? defaultValue = null;
             if (currentIndex <= endIndex &&
                 routeParameter[currentIndex] == '=')
             {

src/Http/Routing/src/LinkGeneratorEndpointNameAddressExtensions.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.Http;
@@ -27,14 +27,14 @@ namespace Microsoft.AspNetCore.Routing
         /// names from <c>RouteOptions</c>.
         /// </param>
         /// <returns>A URI with an absolute path, or <c>null</c>.</returns>
-        public static string GetPathByName(
+        public static string? GetPathByName(
             this LinkGenerator generator,
             HttpContext httpContext,
             string endpointName,
-            object values,
+            object? values,
             PathString? pathBase = default,
             FragmentString fragment = default,
-            LinkOptions options = default)
+            LinkOptions? options = default)
         {
             if (generator == null)
             {
@@ -74,13 +74,13 @@ namespace Microsoft.AspNetCore.Routing
         /// names from <c>RouteOptions</c>.
         /// </param>
         /// <returns>A URI with an absolute path, or <c>null</c>.</returns>
-        public static string GetPathByName(
+        public static string? GetPathByName(
             this LinkGenerator generator,
             string endpointName,
-            object values,
+            object? values,
             PathString pathBase = default,
             FragmentString fragment = default,
-            LinkOptions options = default)
+            LinkOptions? options = default)
         {
             if (generator == null)
             {
@@ -126,16 +126,16 @@ namespace Microsoft.AspNetCore.Routing
         /// your deployment environment.
         /// </para>
         /// </remarks>
-        public static string GetUriByName(
+        public static string? GetUriByName(
             this LinkGenerator generator,
             HttpContext httpContext,
             string endpointName,
-            object values,
+            object? values,
-            string scheme = default,
+            string? scheme = default,
             HostString? host = default,
             PathString? pathBase = default,
             FragmentString fragment = default,
-            LinkOptions options = default)
+            LinkOptions? options = default)
         {
             if (generator == null)
             {
@@ -190,15 +190,15 @@ namespace Microsoft.AspNetCore.Routing
         /// your deployment environment.
         /// </para>
         /// </remarks>
-        public static string GetUriByName(
+        public static string? GetUriByName(
             this LinkGenerator generator,
             string endpointName,
-            object values,
+            object? values,
             string scheme,
             HostString host,
             PathString pathBase = default,
             FragmentString fragment = default,
-            LinkOptions options = default)
+            LinkOptions? options = default)
         {
             if (generator == null)
             {

src/Http/Routing/src/LinkGeneratorRouteValuesAddressExtensions.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.Http;
@@ -27,14 +27,14 @@ namespace Microsoft.AspNetCore.Routing
         /// names from <c>RouteOptions</c>.
         /// </param>
         /// <returns>A URI with an absolute path, or <c>null</c>.</returns>
-        public static string GetPathByRouteValues(
+        public static string? GetPathByRouteValues(
             this LinkGenerator generator,
             HttpContext httpContext,
-            string routeName,
+            string? routeName,
-            object values,
+            object? values,
             PathString? pathBase = default,
             FragmentString fragment = default,
-            LinkOptions options = default)
+            LinkOptions? options = default)
         {
             if (generator == null)
             {
@@ -70,13 +70,13 @@ namespace Microsoft.AspNetCore.Routing
         /// names from <c>RouteOptions</c>.
         /// </param>
         /// <returns>A URI with an absolute path, or <c>null</c>.</returns>
-        public static string GetPathByRouteValues(
+        public static string? GetPathByRouteValues(
             this LinkGenerator generator,
-            string routeName,
+            string? routeName,
-            object values,
+            object? values,
             PathString pathBase = default,
             FragmentString fragment = default,
-            LinkOptions options = default)
+            LinkOptions? options = default)
         {
             if (generator == null)
             {
@@ -118,16 +118,16 @@ namespace Microsoft.AspNetCore.Routing
         /// your deployment environment.
         /// </para>
         /// </remarks>
-        public static string GetUriByRouteValues(
+        public static string? GetUriByRouteValues(
             this LinkGenerator generator,
             HttpContext httpContext,
-            string routeName,
+            string? routeName,
-            object values,
+            object? values,
-            string scheme = default,
+            string? scheme = default,
             HostString? host = default,
             PathString? pathBase = default,
             FragmentString fragment = default,
-            LinkOptions options = default)
+            LinkOptions? options = default)
         {
             if (generator == null)
             {
@@ -178,15 +178,15 @@ namespace Microsoft.AspNetCore.Routing
         /// your deployment environment.
         /// </para>
         /// </remarks>
-        public static string GetUriByRouteValues(
+        public static string? GetUriByRouteValues(
             this LinkGenerator generator,
-            string routeName,
+            string? routeName,
-            object values,
+            object? values,
             string scheme,
             HostString host,
             PathString pathBase = default,
             FragmentString fragment = default,
-            LinkOptions options = default)
+            LinkOptions? options = default)
         {
             if (generator == null)
             {
@@ -197,7 +197,7 @@ namespace Microsoft.AspNetCore.Routing
             return generator.GetUriByAddress<RouteValuesAddress>(address, address.ExplicitValues, scheme, host, pathBase, fragment, options);
         }
 
-        private static RouteValuesAddress CreateAddress(HttpContext httpContext, string routeName, object values)
+        private static RouteValuesAddress CreateAddress(HttpContext? httpContext, string? routeName, object? values)
         {
             return new RouteValuesAddress()
             {

src/Http/Routing/src/LinkParser.cs

@@ -32,6 +32,6 @@ namespace Microsoft.AspNetCore.Routing
         /// of the route patterns match the provided URI path.
         /// </para>
         /// </remarks>
-        public abstract RouteValueDictionary ParsePathByAddress<TAddress>(TAddress address, PathString path);
+        public abstract RouteValueDictionary? ParsePathByAddress<TAddress>(TAddress address, PathString path);
     }
 }

src/Http/Routing/src/LinkParserEndpointNameAddressExtensions.cs

@@ -33,7 +33,7 @@ namespace Microsoft.AspNetCore.Routing
         /// of the route patterns match the provided URI path.
         /// </para>
         /// </remarks>
-        public static RouteValueDictionary ParsePathByEndpointName(
+        public static RouteValueDictionary? ParsePathByEndpointName(
             this LinkParser parser,
             string endpointName,
             PathString path)

src/Http/Routing/src/Logging/RouteConstraintMatcherExtensions.cs

@@ -8,7 +8,7 @@ namespace Microsoft.AspNetCore.Routing.Logging
 {
     internal static class RouteConstraintMatcherExtensions
     {
-        private static readonly Action<ILogger, object, string, IRouteConstraint, Exception> _constraintNotMatched;
+        private static readonly Action<ILogger, object, string, IRouteConstraint, Exception?> _constraintNotMatched;
 
         static RouteConstraintMatcherExtensions()
         {

src/Http/Routing/src/Logging/RouterMiddlewareLoggerExtensions.cs

@@ -8,7 +8,7 @@ namespace Microsoft.AspNetCore.Routing.Logging
 {
     internal static class RouterMiddlewareLoggerExtensions
     {
-        private static readonly Action<ILogger, Exception> _requestNotMatched;
+        private static readonly Action<ILogger, Exception?> _requestNotMatched;
 
         static RouterMiddlewareLoggerExtensions()
         {

src/Http/Routing/src/Logging/TreeRouterLoggerExtensions.cs

@@ -8,7 +8,7 @@ namespace Microsoft.AspNetCore.Routing.Logging
 {
     internal static class TreeRouterLoggerExtensions
     {
-        private static readonly Action<ILogger, string, string, Exception> _requestMatchedRoute;
+        private static readonly Action<ILogger, string, string, Exception?> _requestMatchedRoute;
 
         static TreeRouterLoggerExtensions()
         {

src/Http/Routing/src/MapRouteRouteBuilderExtensions.cs

@@ -154,7 +154,7 @@ namespace Microsoft.AspNetCore.Builder
                     return routeConstraint;
                 }
 
-                var parameterPolicy = _parameterPolicyFactory.Create(null, inlineConstraint);
+                var parameterPolicy = _parameterPolicyFactory.Create(null!, inlineConstraint);
                 if (parameterPolicy != null)
                 {
                     // Logic inside Route will skip adding NullRouteConstraint

src/Http/Routing/src/Matching/CandidateSet.cs

@@ -7,6 +7,7 @@ using System.Collections;
 using System.Collections.Generic;
 using System.Collections.Specialized;
 using System.Diagnostics;
+using System.Diagnostics.CodeAnalysis;
 using System.Linq;
 using System.Runtime.CompilerServices;
 using Microsoft.AspNetCore.Http;
@@ -176,7 +177,7 @@ namespace Microsoft.AspNetCore.Routing.Matching
         /// The <see cref="RouteValueDictionary"/> to replace the original <see cref="RouteValueDictionary"/> at
         /// the <paramref name="index"/>.
         /// </param>
-        public void ReplaceEndpoint(int index, Endpoint endpoint, RouteValueDictionary values)
+        public void ReplaceEndpoint(int index, Endpoint? endpoint, RouteValueDictionary? values)
         {
             // Friendliness for inlining
             if ((uint)index >= Count)
@@ -184,7 +185,9 @@ namespace Microsoft.AspNetCore.Routing.Matching
                 ThrowIndexArgumentOutOfRangeException();
             }
 
-            Candidates[index] = new CandidateState(endpoint, values, Candidates[index].Score);
+            // CandidateState allows a null-valued endpoint. However a validate candidate should never have a null endpoint
+            // We'll make lives easier for matcher policies by declaring it as non-null.
+            Candidates[index] = new CandidateState(endpoint!, values, Candidates[index].Score);
 
             if (endpoint == null)
             {
@@ -354,7 +357,7 @@ namespace Microsoft.AspNetCore.Routing.Matching
                 {
                     if (GetOriginalScore(i) == score)
                     {
-                        duplicates.Add(candidates[i].Endpoint);
+                        duplicates.Add(candidates[i].Endpoint!);
                     }
                 }
 
@@ -366,11 +369,13 @@ namespace Microsoft.AspNetCore.Routing.Matching
             }
         }
 
+        [DoesNotReturn]
         private static void ThrowIndexArgumentOutOfRangeException()
         {
             throw new ArgumentOutOfRangeException("index");
         }
 
+        [DoesNotReturn]
         private static void ThrowArgumentNullException(string parameter)
         {
             throw new ArgumentNullException(parameter);

src/Http/Routing/src/Matching/CandidateState.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.Http;
@@ -17,7 +17,7 @@ namespace Microsoft.AspNetCore.Routing.Matching
             Values = null;
         }
 
-        internal CandidateState(Endpoint endpoint, RouteValueDictionary values, int score)
+        internal CandidateState(Endpoint endpoint, RouteValueDictionary? values, int score)
         {
             Endpoint = endpoint;
             Values = values;
@@ -50,6 +50,6 @@ namespace Microsoft.AspNetCore.Routing.Matching
         /// Gets <see cref="RouteValueDictionary"/> associated with the
         /// <see cref="Http.Endpoint"/> and the current request.
         /// </summary>
-        public RouteValueDictionary Values { get; internal set; }
+        public RouteValueDictionary? Values { get; internal set; }
     }
 }

src/Http/Routing/src/Matching/DataSourceDependentMatcher.cs

@@ -57,10 +57,10 @@ namespace Microsoft.AspNetCore.Routing.Matching
         public sealed class Lifetime : IDisposable
         {
             private readonly object _lock = new object();
-            private DataSourceDependentCache<Matcher> _cache;
+            private DataSourceDependentCache<Matcher>? _cache;
             private bool _disposed;
 
-            public DataSourceDependentCache<Matcher> Cache
+            public DataSourceDependentCache<Matcher>? Cache
             {
                 get => _cache;
                 set

src/Http/Routing/src/Matching/DefaultEndpointSelector.cs

@@ -47,7 +47,7 @@ namespace Microsoft.AspNetCore.Routing.Matching
                         if (CandidateSet.IsValidCandidate(ref state))
                         {
                             httpContext.SetEndpoint(state.Endpoint);
-                            httpContext.Request.RouteValues = state.Values;
+                            httpContext.Request.RouteValues = state.Values!;
                         }
 
                         break;
@@ -67,8 +67,8 @@ namespace Microsoft.AspNetCore.Routing.Matching
             HttpContext httpContext,
             CandidateState[] candidateState)
         {
-            Endpoint endpoint = null;
+            Endpoint? endpoint = null;
-            RouteValueDictionary values = null;
+            RouteValueDictionary? values = null;
             int? foundScore = null;
             for (var i = 0; i < candidateState.Length; i++)
             {
@@ -110,7 +110,7 @@ namespace Microsoft.AspNetCore.Routing.Matching
             if (endpoint != null)
             {
                 httpContext.SetEndpoint(endpoint);
-                httpContext.Request.RouteValues = values;
+                httpContext.Request.RouteValues = values!;
             }
         }
 

src/Http/Routing/src/Matching/DfaMatcher.cs

@@ -40,7 +40,7 @@ namespace Microsoft.AspNetCore.Routing.Matching
             // The sequence of actions we take is optimized to avoid doing expensive work
             // like creating substrings, creating route value dictionaries, and calling
             // into policies like versioning.
-            var path = httpContext.Request.Path.Value;
+            var path = httpContext.Request.Path.Value!;
 
             // First tokenize the path into series of segments.
             Span<PathSegment> buffer = stackalloc PathSegment[_maxSegmentCount];
@@ -119,7 +119,7 @@ namespace Microsoft.AspNetCore.Routing.Matching
                     // We want to create a new array for the route values based on Slots
                     // as a prototype.
                     var prototype = candidate.Slots;
-                    var slots = new KeyValuePair<string, object>[prototype.Length];
+                    var slots = new KeyValuePair<string, object?>[prototype.Length];
 
                     if ((flags & Candidate.CandidateFlags.HasDefaults) != 0)
                     {
@@ -221,7 +221,7 @@ namespace Microsoft.AspNetCore.Routing.Matching
         }
 
         private void ProcessCaptures(
-            KeyValuePair<string, object>[] slots,
+            KeyValuePair<string, object?>[] slots,
             (string parameterName, int segmentIndex, int slotIndex)[] captures,
             string path,
             ReadOnlySpan<PathSegment> segments)
@@ -235,7 +235,7 @@ namespace Microsoft.AspNetCore.Routing.Matching
                     var segment = segments[segmentIndex];
                     if (parameterName != null && segment.Length > 0)
                     {
-                        slots[slotIndex] = new KeyValuePair<string, object>(
+                        slots[slotIndex] = new KeyValuePair<string, object?>(
                             parameterName,
                             path.Substring(segment.Start, segment.Length));
                     }
@@ -244,7 +244,7 @@ namespace Microsoft.AspNetCore.Routing.Matching
         }
 
         private void ProcessCatchAll(
-            KeyValuePair<string, object>[] slots,
+            KeyValuePair<string, object?>[] slots,
             in (string parameterName, int segmentIndex, int slotIndex) catchAll,
             string path,
             ReadOnlySpan<PathSegment> segments)
@@ -255,7 +255,7 @@ namespace Microsoft.AspNetCore.Routing.Matching
             if ((uint)segmentIndex < (uint)segments.Length)
             {
                 var segment = segments[segmentIndex];
-                slots[catchAll.slotIndex] = new KeyValuePair<string, object>(
+                slots[catchAll.slotIndex] = new KeyValuePair<string, object?>(
                     catchAll.parameterName,
                     path.Substring(segment.Start));
             }
@@ -333,6 +333,7 @@ namespace Microsoft.AspNetCore.Routing.Matching
             public static readonly EventId CandidateValid = new EventId(1005, "CandiateValid");
         }
 
+#nullable disable
         private static class Logger
         {
             private static readonly Action<ILogger, string, Exception> _candidatesNotFound = LoggerMessage.Define<string>(

src/Http/Routing/src/Matching/DfaMatcherBuilder.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/Http/Routing/src/Matching/DfaNode.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.Collections.Generic;
 using System.Diagnostics;

src/Http/Routing/src/Matching/EndpointComparer.cs

@@ -38,7 +38,7 @@ namespace Microsoft.AspNetCore.Routing.Matching
             }
         }
 
-        public int Compare(Endpoint x, Endpoint y)
+        public int Compare(Endpoint? x, Endpoint? y)
         {
             // We don't expose this publicly, and we should never call it on
             // a null endpoint.
@@ -74,7 +74,7 @@ namespace Microsoft.AspNetCore.Routing.Matching
             return 0;
         }
 
-        public bool Equals(Endpoint x, Endpoint y)
+        public bool Equals(Endpoint? x, Endpoint? y)
         {
             // We don't expose this publicly, and we should never call it on
             // a null endpoint.
@@ -109,7 +109,7 @@ namespace Microsoft.AspNetCore.Routing.Matching
         {
             public static readonly IComparer<Endpoint> Instance = new OrderComparer();
 
-            public int Compare(Endpoint x, Endpoint y)
+            public int Compare(Endpoint? x, Endpoint? y)
             {
                 var routeEndpointX = x as RouteEndpoint;
                 var routeEndpointY = y as RouteEndpoint;
@@ -136,7 +136,7 @@ namespace Microsoft.AspNetCore.Routing.Matching
         {
             public static readonly IComparer<Endpoint> Instance = new PrecedenceComparer();
 
-            public int Compare(Endpoint x, Endpoint y)
+            public int Compare(Endpoint? x, Endpoint? y)
             {
                 var routeEndpointX = x as RouteEndpoint;
                 var routeEndpointY = y as RouteEndpoint;

src/Http/Routing/src/Matching/HostMatcherPolicy.cs

@@ -342,7 +342,7 @@ namespace Microsoft.AspNetCore.Routing.Matching
 
         private class HostMetadataEndpointComparer : EndpointMetadataComparer<IHostMetadata>
         {
-            protected override int CompareMetadata(IHostMetadata x, IHostMetadata y)
+            protected override int CompareMetadata(IHostMetadata? x, IHostMetadata? y)
             {
                 // Ignore the metadata if it has an empty list of hosts.
                 return base.CompareMetadata(
@@ -391,9 +391,9 @@ namespace Microsoft.AspNetCore.Routing.Matching
             public readonly int? Port;
             public readonly string Host;
 
-            private readonly string _wildcardEndsWith;
+            private readonly string? _wildcardEndsWith;
 
-            public EdgeKey(string host, int? port)
+            public EdgeKey(string? host, int? port)
             {
                 Host = host ?? WildcardHost;
                 Port = port;
@@ -421,9 +421,9 @@ namespace Microsoft.AspNetCore.Routing.Matching
                 return Comparer<int?>.Default.Compare(Port, other.Port);
             }
 
-            public int CompareTo(object obj)
+            public int CompareTo(object? obj)
             {
-                return CompareTo((EdgeKey)obj);
+                return CompareTo((EdgeKey)obj!);
             }
 
             public bool Equals(EdgeKey other)
@@ -437,7 +437,7 @@ namespace Microsoft.AspNetCore.Routing.Matching
                 {
                     if (HasHostWildcard)
                     {
-                        return host.EndsWith(_wildcardEndsWith, StringComparison.OrdinalIgnoreCase);
+                        return host.EndsWith(_wildcardEndsWith!, StringComparison.OrdinalIgnoreCase);
                     }
                     else
                     {
@@ -454,7 +454,7 @@ namespace Microsoft.AspNetCore.Routing.Matching
                 return (Host?.GetHashCode() ?? 0) ^ (Port?.GetHashCode() ?? 0);
             }
 
-            public override bool Equals(object obj)
+            public override bool Equals(object? obj)
             {
                 if (obj is EdgeKey key)
                 {

src/Http/Routing/src/Matching/HttpMethodMatcherPolicy.cs

@@ -108,7 +108,7 @@ namespace Microsoft.AspNetCore.Routing.Matching
             // We want to return a 405 iff we eliminated ALL of the currently valid endpoints due to HTTP method
             // mismatch.
             bool? needs405Endpoint = null;
-            HashSet<string> methods = null;
+            HashSet<string>? methods = null;
 
             for (var i = 0; i < candidates.Count; i++)
             {
@@ -168,8 +168,8 @@ namespace Microsoft.AspNetCore.Routing.Matching
             if (needs405Endpoint == true)
             {
                 // We saw some endpoints coming in, and we eliminated them all.
-                httpContext.SetEndpoint(CreateRejectionEndpoint(methods.OrderBy(m => m, StringComparer.OrdinalIgnoreCase)));
+                httpContext.SetEndpoint(CreateRejectionEndpoint(methods!.OrderBy(m => m, StringComparer.OrdinalIgnoreCase)));
-                httpContext.Request.RouteValues = null;
+                httpContext.Request.RouteValues = null!;
             }
 
             return Task.CompletedTask;
@@ -329,8 +329,8 @@ namespace Microsoft.AspNetCore.Routing.Matching
         /// <returns></returns>
         public PolicyJumpTable BuildJumpTable(int exitDestination, IReadOnlyList<PolicyJumpTableEdge> edges)
         {
-            Dictionary<string, int> destinations = null;
+            Dictionary<string, int>? destinations = null;
-            Dictionary<string, int> corsPreflightDestinations = null;
+            Dictionary<string, int>? corsPreflightDestinations = null;
             for (var i = 0; i < edges.Count; i++)
             {
                 // We create this data, so it's safe to cast it.
@@ -421,17 +421,17 @@ namespace Microsoft.AspNetCore.Routing.Matching
         private class HttpMethodPolicyJumpTable : PolicyJumpTable
         {
             private readonly int _exitDestination;
-            private readonly Dictionary<string, int> _destinations;
+            private readonly Dictionary<string, int>? _destinations;
             private readonly int _corsPreflightExitDestination;
-            private readonly Dictionary<string, int> _corsPreflightDestinations;
+            private readonly Dictionary<string, int>? _corsPreflightDestinations;
 
             private readonly bool _supportsCorsPreflight;
 
             public HttpMethodPolicyJumpTable(
                 int exitDestination,
-                Dictionary<string, int> destinations,
+                Dictionary<string, int>? destinations,
                 int corsPreflightExitDestination,
-                Dictionary<string, int> corsPreflightDestinations)
+                Dictionary<string, int>? corsPreflightDestinations)
             {
                 _exitDestination = exitDestination;
                 _destinations = destinations;
@@ -466,7 +466,7 @@ namespace Microsoft.AspNetCore.Routing.Matching
 
         private class HttpMethodMetadataEndpointComparer : EndpointMetadataComparer<IHttpMethodMetadata>
         {
-            protected override int CompareMetadata(IHttpMethodMetadata x, IHttpMethodMetadata y)
+            protected override int CompareMetadata(IHttpMethodMetadata? x, IHttpMethodMetadata? y)
             {
                 // Ignore the metadata if it has an empty list of HTTP methods.
                 return base.CompareMetadata(
@@ -501,9 +501,9 @@ namespace Microsoft.AspNetCore.Routing.Matching
                 return IsCorsPreflightRequest.CompareTo(other.IsCorsPreflightRequest);
             }
 
-            public int CompareTo(object obj)
+            public int CompareTo(object? obj)
             {
-                return CompareTo((EdgeKey)obj);
+                return CompareTo((EdgeKey)obj!);
             }
 
             public bool Equals(EdgeKey other)
@@ -513,7 +513,7 @@ namespace Microsoft.AspNetCore.Routing.Matching
                     HttpMethods.Equals(HttpMethod, other.HttpMethod);
             }
 
-            public override bool Equals(object obj)
+            public override bool Equals(object? obj)
             {
                 var other = obj as EdgeKey?;
                 return other == null ? false : Equals(other.Value);

src/Http/Routing/src/Matching/ILEmitTrieFactory.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.Diagnostics;
 using System.Linq;

src/Http/Routing/src/Matching/ILEmitTrieJumpTable.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.Threading;
 using System.Threading.Tasks;

src/Http/Routing/src/Matching/PathSegment.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.Routing.Matching
             Length = length;
         }
 
-        public override bool Equals(object obj)
+        public override bool Equals(object? obj)
         {
             return obj is PathSegment segment ? Equals(segment) : false;
         }

src/Http/Routing/src/Microsoft.AspNetCore.Routing.csproj

@@ -12,7 +12,7 @@ Microsoft.AspNetCore.Routing.RouteCollection</Description>
     <PackageTags>aspnetcore;routing</PackageTags>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
     <IsPackable>false</IsPackable>
-    <Nullable>annotations</Nullable>
+    <Nullable>enable</Nullable>
   </PropertyGroup>
 
   <PropertyGroup>

src/Http/Routing/src/NullRouter.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.Threading.Tasks;
@@ -13,7 +13,7 @@ namespace Microsoft.AspNetCore.Routing
         {
         }
 
-        public VirtualPathData GetVirtualPath(VirtualPathContext context)
+        public VirtualPathData? GetVirtualPath(VirtualPathContext context)
         {
             return null;
         }

src/Http/Routing/src/ParameterPolicyActivator.cs

@@ -1,12 +1,13 @@
 // 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.Globalization;
 using System.Linq;
 using System.Reflection;
-using System.Text;
 using Microsoft.Extensions.DependencyInjection;
 
 namespace Microsoft.AspNetCore.Routing

src/Http/Routing/src/ParameterPolicyFactory.cs

@@ -26,7 +26,7 @@ namespace Microsoft.AspNetCore.Routing
         /// <param name="parameter">The parameter the parameter policy is being created for.</param>
         /// <param name="parameterPolicy">An existing parameter policy.</param>
         /// <returns>The <see cref="IParameterPolicy"/> for the parameter.</returns>
-        public abstract IParameterPolicy Create(RoutePatternParameterPart parameter, IParameterPolicy parameterPolicy);
+        public abstract IParameterPolicy Create(RoutePatternParameterPart? parameter, IParameterPolicy parameterPolicy);
 
         /// <summary>
         /// Creates a parameter policy.
@@ -34,7 +34,7 @@ namespace Microsoft.AspNetCore.Routing
         /// <param name="parameter">The parameter the parameter policy is being created for.</param>
         /// <param name="reference">The reference to resolve.</param>
         /// <returns>The <see cref="IParameterPolicy"/> for the parameter.</returns>
-        public IParameterPolicy Create(RoutePatternParameterPart parameter, RoutePatternParameterPolicyReference reference)
+        public IParameterPolicy Create(RoutePatternParameterPart? parameter, RoutePatternParameterPolicyReference reference)
         {
             if (reference == null)
             {

src/Http/Routing/src/PathTokenizer.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/Http/Routing/src/Patterns/DefaultRoutePatternTransformer.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;
 

src/Http/Routing/src/Patterns/RouteParameterParser.cs

@@ -78,7 +78,7 @@ namespace Microsoft.AspNetCore.Routing.Patterns
             var parseResults = ParseConstraints(parameter, currentIndex, endIndex);
             currentIndex = parseResults.CurrentIndex;
 
-            string defaultValue = null;
+            string? defaultValue = null;
             if (currentIndex <= endIndex &&
                 parameter[currentIndex] == '=')
             {

src/Http/Routing/src/Patterns/RoutePattern.cs

@@ -27,7 +27,7 @@ namespace Microsoft.AspNetCore.Routing.Patterns
         /// </remarks>
         public static readonly object RequiredValueAny = new RequiredValueAnySentinal();
 
-        internal static bool IsRequiredValueAny(object value)
+        internal static bool IsRequiredValueAny(object? value)
         {
             return object.ReferenceEquals(RequiredValueAny, value);
         }
@@ -35,10 +35,10 @@ namespace Microsoft.AspNetCore.Routing.Patterns
         private const string SeparatorString = "/";
 
         internal RoutePattern(
-            string rawText,
+            string? rawText,
-            IReadOnlyDictionary<string, object> defaults,
+            IReadOnlyDictionary<string, object?> defaults,
             IReadOnlyDictionary<string, IReadOnlyList<RoutePatternParameterPolicyReference>> parameterPolicies,
-            IReadOnlyDictionary<string, object> requiredValues,
+            IReadOnlyDictionary<string, object?> requiredValues,
             IReadOnlyList<RoutePatternParameterPart> parameters,
             IReadOnlyList<RoutePatternPathSegment> pathSegments)
         {
@@ -63,7 +63,7 @@ namespace Microsoft.AspNetCore.Routing.Patterns
         /// Gets the set of default values for the route pattern.
         /// The keys of <see cref="Defaults"/> are the route parameter names.
         /// </summary>
-        public IReadOnlyDictionary<string, object> Defaults { get; }
+        public IReadOnlyDictionary<string, object?> Defaults { get; }
 
         /// <summary>
         /// Gets the set of parameter policy references for the route pattern.
@@ -92,7 +92,7 @@ namespace Microsoft.AspNetCore.Routing.Patterns
         /// </example>
         /// </para>
         /// </remarks>
-        public IReadOnlyDictionary<string, object> RequiredValues { get; }
+        public IReadOnlyDictionary<string, object?> RequiredValues { get; }
 
         /// <summary>
         /// Gets the precedence value of the route pattern for URL matching.
@@ -115,7 +115,7 @@ namespace Microsoft.AspNetCore.Routing.Patterns
         /// <summary>
         /// Gets the raw text supplied when parsing the route pattern. May be null.
         /// </summary>
-        public string RawText { get; }
+        public string? RawText { get; }
 
         /// <summary>
         /// Gets the list of route parameters.
@@ -132,7 +132,7 @@ namespace Microsoft.AspNetCore.Routing.Patterns
         /// </summary>
         /// <param name="name">The name of the parameter to match.</param>
         /// <returns>The matching parameter or <c>null</c> if no parameter matches the given name.</returns>
-        public RoutePatternParameterPart GetParameter(string name)
+        public RoutePatternParameterPart? GetParameter(string name)
         {
             if (name == null)
             {

src/Http/Routing/src/Patterns/RoutePatternException.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;
@@ -15,7 +15,7 @@ namespace Microsoft.AspNetCore.Routing.Patterns
         private RoutePatternException(SerializationInfo info, StreamingContext context)
             : base(info, context)
         {
-            Pattern = (string)info.GetValue(nameof(Pattern), typeof(string));
+            Pattern = (string)info.GetValue(nameof(Pattern), typeof(string))!;
         }
 
         /// <summary>

src/Http/Routing/src/Patterns/RoutePatternFactory.cs

@@ -17,8 +17,8 @@ namespace Microsoft.AspNetCore.Routing.Patterns
     /// </summary>
     public static class RoutePatternFactory
     {
-        private static readonly IReadOnlyDictionary<string, object> EmptyDictionary =
+        private static readonly IReadOnlyDictionary<string, object?> EmptyDictionary =
-            new ReadOnlyDictionary<string, object>(new Dictionary<string, object>());
+            new ReadOnlyDictionary<string, object?>(new Dictionary<string, object?>());
 
         private static readonly IReadOnlyDictionary<string, IReadOnlyList<RoutePatternParameterPolicyReference>> EmptyPoliciesDictionary =
             new ReadOnlyDictionary<string, IReadOnlyList<RoutePatternParameterPolicyReference>>(new Dictionary<string, IReadOnlyList<RoutePatternParameterPolicyReference>>());
@@ -55,7 +55,7 @@ namespace Microsoft.AspNetCore.Routing.Patterns
         /// Multiple policies can be specified for a key by providing a collection as the value.
         /// </param>
         /// <returns>The <see cref="RoutePattern"/>.</returns>
-        public static RoutePattern Parse(string pattern, object defaults, object parameterPolicies)
+        public static RoutePattern Parse(string pattern, object? defaults, object? parameterPolicies)
         {
             if (pattern == null)
             {
@@ -86,7 +86,7 @@ namespace Microsoft.AspNetCore.Routing.Patterns
         /// Route values that can be substituted for parameters in the route pattern. See remarks on <see cref="RoutePattern.RequiredValues"/>.
         /// </param>
         /// <returns>The <see cref="RoutePattern"/>.</returns>
-        public static RoutePattern Parse(string pattern, object defaults, object parameterPolicies, object requiredValues)
+        public static RoutePattern Parse(string pattern, object? defaults, object? parameterPolicies, object? requiredValues)
         {
             if (pattern == null)
             {
@@ -118,7 +118,7 @@ namespace Microsoft.AspNetCore.Routing.Patterns
         /// <param name="rawText">The raw text to associate with the route pattern. May be null.</param>
         /// <param name="segments">The collection of segments.</param>
         /// <returns>The <see cref="RoutePattern"/>.</returns>
-        public static RoutePattern Pattern(string rawText, IEnumerable<RoutePatternPathSegment> segments)
+        public static RoutePattern Pattern(string? rawText, IEnumerable<RoutePatternPathSegment> segments)
         {
             if (segments == null)
             {
@@ -146,8 +146,8 @@ namespace Microsoft.AspNetCore.Routing.Patterns
         /// <param name="segments">The collection of segments.</param>
         /// <returns>The <see cref="RoutePattern"/>.</returns>
         public static RoutePattern Pattern(
-            object defaults,
+            object? defaults,
-            object parameterPolicies,
+            object? parameterPolicies,
             IEnumerable<RoutePatternPathSegment> segments)
         {
             if (segments == null)
@@ -177,9 +177,9 @@ namespace Microsoft.AspNetCore.Routing.Patterns
         /// <param name="segments">The collection of segments.</param>
         /// <returns>The <see cref="RoutePattern"/>.</returns>
         public static RoutePattern Pattern(
-            string rawText,
+            string? rawText,
-            object defaults,
+            object? defaults,
-            object parameterPolicies,
+            object? parameterPolicies,
             IEnumerable<RoutePatternPathSegment> segments)
         {
             if (segments == null)
@@ -239,8 +239,8 @@ namespace Microsoft.AspNetCore.Routing.Patterns
         /// <param name="segments">The collection of segments.</param>
         /// <returns>The <see cref="RoutePattern"/>.</returns>
         public static RoutePattern Pattern(
-            object defaults,
+            object? defaults,
-            object parameterPolicies,
+            object? parameterPolicies,
             params RoutePatternPathSegment[] segments)
         {
             if (segments == null)
@@ -270,9 +270,9 @@ namespace Microsoft.AspNetCore.Routing.Patterns
         /// <param name="segments">The collection of segments.</param>
         /// <returns>The <see cref="RoutePattern"/>.</returns>
         public static RoutePattern Pattern(
-            string rawText,
+            string? rawText,
-            object defaults,
+            object? defaults,
-            object parameterPolicies,
+            object? parameterPolicies,
             params RoutePatternPathSegment[] segments)
         {
             if (segments == null)
@@ -284,10 +284,10 @@ namespace Microsoft.AspNetCore.Routing.Patterns
         }
 
         private static RoutePattern PatternCore(
-            string rawText,
+            string? rawText,
-            RouteValueDictionary defaults,
+            RouteValueDictionary? defaults,
-            RouteValueDictionary parameterPolicies,
+            RouteValueDictionary? parameterPolicies,
-            RouteValueDictionary requiredValues,
+            RouteValueDictionary? requiredValues,
             IEnumerable<RoutePatternPathSegment> segments)
         {
             // We want to merge the segment data with the 'out of line' defaults and parameter policies.
@@ -301,10 +301,10 @@ namespace Microsoft.AspNetCore.Routing.Patterns
             // It's important that these two views of the data are consistent. We don't want
             // values specified out of line to have a different behavior.
 
-            Dictionary<string, object> updatedDefaults = null;
+            Dictionary<string, object?>? updatedDefaults = null;
             if (defaults != null && defaults.Count > 0)
             {
-                updatedDefaults = new Dictionary<string, object>(defaults.Count, StringComparer.OrdinalIgnoreCase);
+                updatedDefaults = new Dictionary<string, object?>(defaults.Count, StringComparer.OrdinalIgnoreCase);
 
                 foreach (var kvp in defaults)
                 {
@@ -312,7 +312,7 @@ namespace Microsoft.AspNetCore.Routing.Patterns
                 }
             }
 
-            Dictionary<string, List<RoutePatternParameterPolicyReference>> updatedParameterPolicies = null;
+            Dictionary<string, List<RoutePatternParameterPolicyReference>>? updatedParameterPolicies = null;
             if (parameterPolicies != null && parameterPolicies.Count > 0)
             {
                 updatedParameterPolicies = new Dictionary<string, List<RoutePatternParameterPolicyReference>>(parameterPolicies.Count, StringComparer.OrdinalIgnoreCase);
@@ -349,7 +349,7 @@ namespace Microsoft.AspNetCore.Routing.Patterns
                 }
             }
 
-            List<RoutePatternParameterPart> parameters = null;
+            List<RoutePatternParameterPart>? parameters = null;
             var updatedSegments = segments.ToArray();
             for (var i = 0; i < updatedSegments.Length; i++)
             {
@@ -420,12 +420,12 @@ namespace Microsoft.AspNetCore.Routing.Patterns
                     ? updatedParameterPolicies.ToDictionary(kvp => kvp.Key, kvp => (IReadOnlyList<RoutePatternParameterPolicyReference>)kvp.Value.ToArray())
                     : EmptyPoliciesDictionary,
                 requiredValues ?? EmptyDictionary,
-                (IReadOnlyList<RoutePatternParameterPart>)parameters ?? Array.Empty<RoutePatternParameterPart>(),
+                (IReadOnlyList<RoutePatternParameterPart>?)parameters ?? Array.Empty<RoutePatternParameterPart>(),
                 updatedSegments);
 
             RoutePatternPathSegment VisitSegment(RoutePatternPathSegment segment)
             {
-                RoutePatternPart[] updatedParts = null;
+                RoutePatternPart[]? updatedParts = null;
                 for (var i = 0; i < segment.Parts.Count; i++)
                 {
                     var part = segment.Parts[i];
@@ -482,13 +482,13 @@ namespace Microsoft.AspNetCore.Routing.Patterns
                 {
                     if (updatedDefaults == null)
                     {
-                        updatedDefaults = new Dictionary<string, object>(StringComparer.OrdinalIgnoreCase);
+                        updatedDefaults = new Dictionary<string, object?>(StringComparer.OrdinalIgnoreCase);
                     }
 
                     updatedDefaults[parameter.Name] = parameter.Default;
                 }
 
-                List<RoutePatternParameterPolicyReference> parameterConstraints = null;
+                List<RoutePatternParameterPolicyReference>? parameterConstraints = null;
                 if ((updatedParameterPolicies == null || !updatedParameterPolicies.TryGetValue(parameter.Name, out parameterConstraints)) &&
                     parameter.ParameterPolicies.Count > 0)
                 {
@@ -503,7 +503,7 @@ namespace Microsoft.AspNetCore.Routing.Patterns
 
                 if (parameter.ParameterPolicies.Count > 0)
                 {
-                    parameterConstraints.AddRange(parameter.ParameterPolicies);
+                    parameterConstraints!.AddRange(parameter.ParameterPolicies);
                 }
 
                 if (Equals(parameter.Default, @default)
@@ -667,7 +667,7 @@ namespace Microsoft.AspNetCore.Routing.Patterns
         /// <returns>The <see cref="RoutePatternParameterPart"/>.</returns>
         public static RoutePatternParameterPart ParameterPart(
             string parameterName,
-            object @default,
+            object? @default,
             RoutePatternParameterKind parameterKind)
         {
             if (string.IsNullOrEmpty(parameterName))
@@ -703,7 +703,7 @@ namespace Microsoft.AspNetCore.Routing.Patterns
         /// <returns>The <see cref="RoutePatternParameterPart"/>.</returns>
         public static RoutePatternParameterPart ParameterPart(
             string parameterName,
-            object @default,
+            object? @default,
             RoutePatternParameterKind parameterKind,
             IEnumerable<RoutePatternParameterPolicyReference> parameterPolicies)
         {
@@ -745,7 +745,7 @@ namespace Microsoft.AspNetCore.Routing.Patterns
         /// <returns>The <see cref="RoutePatternParameterPart"/>.</returns>
         public static RoutePatternParameterPart ParameterPart(
             string parameterName,
-            object @default,
+            object? @default,
             RoutePatternParameterKind parameterKind,
             params RoutePatternParameterPolicyReference[] parameterPolicies)
         {
@@ -778,7 +778,7 @@ namespace Microsoft.AspNetCore.Routing.Patterns
 
         private static RoutePatternParameterPart ParameterPartCore(
             string parameterName,
-            object @default,
+            object? @default,
             RoutePatternParameterKind parameterKind,
             RoutePatternParameterPolicyReference[] parameterPolicies)
         {
@@ -787,7 +787,7 @@ namespace Microsoft.AspNetCore.Routing.Patterns
 
         private static RoutePatternParameterPart ParameterPartCore(
             string parameterName,
-            object @default,
+            object? @default,
             RoutePatternParameterKind parameterKind,
             RoutePatternParameterPolicyReference[] parameterPolicies,
             bool encodeSlashes)
@@ -906,7 +906,7 @@ namespace Microsoft.AspNetCore.Routing.Patterns
             return new RoutePatternParameterPolicyReference(parameterPolicy);
         }
 
-        private static RouteValueDictionary Wrap(object values)
+        private static RouteValueDictionary? Wrap(object? values)
         {
             return values == null ? null : new RouteValueDictionary(values);
         }

src/Http/Routing/src/Patterns/RoutePatternMatcher.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.Diagnostics;
 using Microsoft.AspNetCore.Http;

src/Http/Routing/src/Patterns/RoutePatternParameterPart.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.Collections.Generic;
@@ -16,7 +16,7 @@ namespace Microsoft.AspNetCore.Routing.Patterns
     {
         internal RoutePatternParameterPart(
             string parameterName,
-            object @default,
+            object? @default,
             RoutePatternParameterKind parameterKind,
             RoutePatternParameterPolicyReference[] parameterPolicies)
             : this(parameterName, @default, parameterKind, parameterPolicies, encodeSlashes: true)
@@ -25,7 +25,7 @@ namespace Microsoft.AspNetCore.Routing.Patterns
 
         internal RoutePatternParameterPart(
             string parameterName,
-            object @default,
+            object? @default,
             RoutePatternParameterKind parameterKind,
             RoutePatternParameterPolicyReference[] parameterPolicies,
             bool encodeSlashes)
@@ -53,7 +53,7 @@ namespace Microsoft.AspNetCore.Routing.Patterns
         /// <summary>
         /// Gets the default value of this route parameter. May be null.
         /// </summary>
-        public object Default { get; }
+        public object? Default { get; }
 
         /// <summary>
         /// Returns <c>true</c> if this part is a catch-all parameter.

src/Http/Routing/src/Patterns/RoutePatternParameterPolicyReference.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.Diagnostics;
@@ -26,14 +26,14 @@ namespace Microsoft.AspNetCore.Routing.Patterns
         /// <summary>
         /// Gets the constraint text.
         /// </summary>
-        public string Content { get; }
+        public string? Content { get; }
 
         /// <summary>
         /// Gets a pre-existing <see cref="IParameterPolicy"/> that was used to construct this reference.
         /// </summary>
-        public IParameterPolicy ParameterPolicy { get; }
+        public IParameterPolicy? ParameterPolicy { get; }
 
-        private string DebuggerToString()
+        private string? DebuggerToString()
         {
             return Content;
         }

src/Http/Routing/src/Patterns/RoutePatternParser.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/Http/Routing/src/Patterns/RoutePatternTransformer.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.Routing.Patterns
@@ -30,6 +30,6 @@ namespace Microsoft.AspNetCore.Routing.Patterns
         /// return <c>null</c> if any required value cannot be substituted.
         /// </para>
         /// </remarks>
-        public abstract RoutePattern SubstituteRequiredValues(RoutePattern original, object requiredValues);
+        public abstract RoutePattern? SubstituteRequiredValues(RoutePattern original, object requiredValues);
     }
 }

src/Http/Routing/src/RequestDelegateRouteBuilderExtensions.cs

@@ -259,7 +259,7 @@ namespace Microsoft.AspNetCore.Routing
                 new RouteHandler(handler),
                 template,
                 defaults: null,
-                constraints: new RouteValueDictionary(new { httpMethod = new HttpMethodRouteConstraint(verb) }),
+                constraints: new RouteValueDictionary(new { httpMethod = new HttpMethodRouteConstraint(verb) })!,
                 dataTokens: null,
                 inlineConstraintResolver: GetConstraintResolver(builder));
 

src/Http/Routing/src/Route.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.Collections.Generic;
 using System.Threading.Tasks;
@@ -62,7 +60,7 @@ namespace Microsoft.AspNetCore.Routing
             _target = target;
         }
 
-        public string RouteTemplate => ParsedTemplate.TemplateText;
+        public string? RouteTemplate => ParsedTemplate.TemplateText;
 
         protected override Task OnRouteMatched(RouteContext context)
         {

src/Http/Routing/src/RouteBase.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.Collections.Generic;
 using System.Diagnostics;
@@ -110,7 +108,7 @@ namespace Microsoft.AspNetCore.Routing
             {
                 return Task.CompletedTask;
             }
-            _logger.RequestMatchedRoute(Name!, ParsedTemplate.TemplateText);
+            _logger.RequestMatchedRoute(Name!, ParsedTemplate.TemplateText!);
 
             return OnRouteMatched(context);
         }
@@ -175,7 +173,7 @@ namespace Microsoft.AspNetCore.Routing
             RouteTemplate parsedTemplate,
             IDictionary<string, object>? constraints)
         {
-            var constraintBuilder = new RouteConstraintBuilder(inlineConstraintResolver, parsedTemplate.TemplateText);
+            var constraintBuilder = new RouteConstraintBuilder(inlineConstraintResolver, parsedTemplate.TemplateText!);
 
             if (constraints != null)
             {
@@ -189,12 +187,12 @@ namespace Microsoft.AspNetCore.Routing
             {
                 if (parameter.IsOptional)
                 {
-                    constraintBuilder.SetOptional(parameter.Name);
+                    constraintBuilder.SetOptional(parameter.Name!);
                 }
 
                 foreach (var inlineConstraint in parameter.InlineConstraints)
                 {
-                    constraintBuilder.AddResolvedConstraint(parameter.Name, inlineConstraint.Constraint);
+                    constraintBuilder.AddResolvedConstraint(parameter.Name!, inlineConstraint.Constraint);
                 }
             }
 
@@ -219,7 +217,7 @@ namespace Microsoft.AspNetCore.Routing
                               parameter.Name));
                     }
 #else
-                    if (result.ContainsKey(parameter.Name))
+                    if (result.ContainsKey(parameter.Name!))
                     {
                         throw new InvalidOperationException(
                           Resources.FormatTemplateRoute_CannotHaveDefaultValueSpecifiedInlineAndExplicitly(
@@ -227,7 +225,7 @@ namespace Microsoft.AspNetCore.Routing
                     }
                     else
                     {
-                        result.Add(parameter.Name, parameter.DefaultValue);
+                        result.Add(parameter.Name!, parameter.DefaultValue);
                     }
 #endif
                 }
@@ -300,7 +298,7 @@ namespace Microsoft.AspNetCore.Routing
 
         public override string ToString()
         {
-            return ParsedTemplate.TemplateText;
+            return ParsedTemplate.TemplateText!;
         }
     }
 }

src/Http/Routing/src/RouteConstraintMatcher.cs

@@ -53,7 +53,7 @@ namespace Microsoft.AspNetCore.Routing
                     {
                         routeValues.TryGetValue(kvp.Key, out var routeValue);
 
-                        logger.ConstraintNotMatched(routeValue, kvp.Key, kvp.Value);
+                        logger.ConstraintNotMatched(routeValue!, kvp.Key, kvp.Value);
                     }
 
                     return false;

src/Http/Routing/src/RouteEndpoint.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;
@@ -28,8 +28,8 @@ namespace Microsoft.AspNetCore.Routing
             RequestDelegate requestDelegate,
             RoutePattern routePattern,
             int order,
-            EndpointMetadataCollection metadata,
+            EndpointMetadataCollection? metadata,
-            string displayName)
+            string? displayName)
             : base(requestDelegate, metadata, displayName)
         {
             if (requestDelegate == null)

src/Http/Routing/src/RouteEndpointBuilder.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 Microsoft.AspNetCore.Builder;
 using Microsoft.AspNetCore.Http;
 using Microsoft.AspNetCore.Routing.Patterns;
@@ -25,6 +26,11 @@ namespace Microsoft.AspNetCore.Routing
 
         public override Endpoint Build()
         {
+            if (RequestDelegate is null)
+            {
+                throw new InvalidOperationException($"{nameof(RequestDelegate)} must be specified to construct a {nameof(RouteEndpoint)}.");
+            }
+
             var routeEndpoint = new RouteEndpoint(
                 RequestDelegate,
                 RoutePattern,

src/Http/Routing/src/RouteOptions.cs

@@ -11,7 +11,7 @@ namespace Microsoft.AspNetCore.Routing
     public class RouteOptions
     {
         private IDictionary<string, Type> _constraintTypeMap = GetDefaultConstraintMap();
-        private ICollection<EndpointDataSource> _endpointDataSources;
+        private ICollection<EndpointDataSource> _endpointDataSources = default!;
 
         /// <summary>
         /// Gets a collection of <see cref="EndpointDataSource"/> instances configured with routing.

src/Http/Routing/src/RouteValueEqualityComparer.cs

@@ -18,12 +18,12 @@ namespace Microsoft.AspNetCore.Routing
     ///
     /// strings are compared using <see cref="StringComparison.OrdinalIgnoreCase"/>.
     /// </remarks>
-    public class RouteValueEqualityComparer : IEqualityComparer<object>
+    public class RouteValueEqualityComparer : IEqualityComparer<object?>
     {
         public static readonly RouteValueEqualityComparer Default = new RouteValueEqualityComparer();
 
         /// <inheritdoc />
-        public new bool Equals(object x, object y)
+        public new bool Equals(object? x, object? y)
         {
             var stringX = x as string ?? Convert.ToString(x, CultureInfo.InvariantCulture);
             var stringY = y as string ?? Convert.ToString(y, CultureInfo.InvariantCulture);

src/Http/Routing/src/RouteValuesAddressScheme.cs

@@ -30,7 +30,7 @@ namespace Microsoft.AspNetCore.Routing
 
             var state = State;
 
-            IList<OutboundMatchResult> matchResults = null;
+            IList<OutboundMatchResult>? matchResults = null;
             if (string.IsNullOrEmpty(address.RouteName))
             {
                 matchResults = state.AllMatchesLinkGenerationTree.GetMatches(
@@ -141,8 +141,8 @@ namespace Microsoft.AspNetCore.Routing
 
         private OutboundRouteEntry CreateOutboundRouteEntry(
             RouteEndpoint endpoint,
-            IReadOnlyDictionary<string, object> requiredValues,
+            IReadOnlyDictionary<string, object?> requiredValues,
-            string routeName)
+            string? routeName)
         {
             var entry = new OutboundRouteEntry()
             {

src/Http/Routing/src/Template/InlineConstraint.cs

@@ -32,7 +32,7 @@ namespace Microsoft.AspNetCore.Routing.Template
                 throw new ArgumentNullException(nameof(other));
             }
 
-            Constraint = other.Content;
+            Constraint = other.Content!;
         }
 
         /// <summary>

src/Http/Routing/src/Template/RouteTemplate.cs

@@ -68,7 +68,7 @@ namespace Microsoft.AspNetCore.Routing.Template
             }
         }
 
-        public string TemplateText { get; }
+        public string? TemplateText { get; }
 
         public IList<TemplatePart> Parameters { get; }
 

src/Http/Routing/src/Template/TemplateBinder.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.Collections;
 using System.Collections.Generic;

src/Http/Routing/src/Template/TemplateMatcher.cs

@@ -51,7 +51,7 @@ namespace Microsoft.AspNetCore.Routing.Template
                     continue;
                 }
 
-                if (Defaults.TryGetValue(part.Name, out var value))
+                if (Defaults.TryGetValue(part.Name!, out var value))
                 {
                     _hasDefaultValue[i] = true;
                     _defaultValues[i] = value;

src/Http/Routing/src/Template/TemplatePart.cs

@@ -4,6 +4,7 @@
 using System;
 using System.Collections.Generic;
 using System.Diagnostics;
+using System.Diagnostics.CodeAnalysis;
 using System.Linq;
 using Microsoft.AspNetCore.Routing.Patterns;
 
@@ -32,7 +33,7 @@ namespace Microsoft.AspNetCore.Routing.Template
                 IsCatchAll = parameter.IsCatchAll;
                 IsOptional = parameter.IsOptional;
                 DefaultValue = parameter.Default;
-                InlineConstraints = parameter.ParameterPolicies?.Select(p => new InlineConstraint(p));
+                InlineConstraints = parameter.ParameterPolicies?.Select(p => new InlineConstraint(p)) ?? Enumerable.Empty<InlineConstraint>();
             }
             else if (other.IsSeparator && other is RoutePatternSeparatorPart separator)
             {
@@ -59,8 +60,8 @@ namespace Microsoft.AspNetCore.Routing.Template
             string name,
             bool isCatchAll,
             bool isOptional,
-            object defaultValue,
+            object? defaultValue,
-            IEnumerable<InlineConstraint> inlineConstraints)
+            IEnumerable<InlineConstraint>? inlineConstraints)
         {
             if (name == null)
             {
@@ -83,12 +84,12 @@ namespace Microsoft.AspNetCore.Routing.Template
         public bool IsParameter { get; private set; }
         public bool IsOptional { get; private set; }
         public bool IsOptionalSeperator { get; set; }
-        public string Name { get; private set; }
+        public string? Name { get; private set; }
-        public string Text { get; private set; }
+        public string? Text { get; private set; }
-        public object DefaultValue { get; private set; }
+        public object? DefaultValue { get; private set; }
-        public IEnumerable<InlineConstraint> InlineConstraints { get; private set; }
+        public IEnumerable<InlineConstraint> InlineConstraints { get; private set; } = Enumerable.Empty<InlineConstraint>();
 
-        internal string DebuggerToString()
+        internal string? DebuggerToString()
         {
             if (IsParameter)
             {
@@ -104,11 +105,11 @@ namespace Microsoft.AspNetCore.Routing.Template
         {
             if (IsLiteral && IsOptionalSeperator)
             {
-                return RoutePatternFactory.SeparatorPart(Text);
+                return RoutePatternFactory.SeparatorPart(Text!);
             }
             else if (IsLiteral)
             {
-                return RoutePatternFactory.LiteralPart(Text);
+                return RoutePatternFactory.LiteralPart(Text!);
             }
             else
             {
@@ -119,7 +120,7 @@ namespace Microsoft.AspNetCore.Routing.Template
                         RoutePatternParameterKind.Standard;
 
                 var constraints = InlineConstraints.Select(c => new RoutePatternParameterPolicyReference(c.Constraint));
-                return RoutePatternFactory.ParameterPart(Name, DefaultValue, kind, constraints);
+                return RoutePatternFactory.ParameterPart(Name!, DefaultValue, kind, constraints);
             }
         }
     }

src/Http/Routing/src/Template/TemplateValuesResult.cs

@@ -11,7 +11,7 @@ namespace Microsoft.AspNetCore.Routing.Template
         /// <summary>
         /// The set of values that will appear in the URL.
         /// </summary>
-        public RouteValueDictionary AcceptedValues { get; set; }
+        public RouteValueDictionary AcceptedValues { get; set; } = default!;
 
         /// <summary>
         /// The set of values that that were supplied for URL generation.
@@ -24,6 +24,6 @@ namespace Microsoft.AspNetCore.Routing.Template
         /// Implicit (ambient) values which are invalidated due to changes in values lexically earlier in the
         /// route template are excluded from this set.
         /// </remarks>
-        public RouteValueDictionary CombinedValues { get; set; }
+        public RouteValueDictionary CombinedValues { get; set; } = default!;
     }
 }

src/Http/Routing/src/Tree/InboundMatch.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.Diagnostics;
 using Microsoft.AspNetCore.Routing.Template;
 

src/Http/Routing/src/Tree/InboundRouteEntry.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 Microsoft.AspNetCore.Routing.Template;
 

src/Http/Routing/src/Tree/LinkGenerationDecisionTree.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/Http/Routing/src/Tree/OutboundMatch.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 Microsoft.AspNetCore.Routing.Template;
 
 namespace Microsoft.AspNetCore.Routing.Tree

src/Http/Routing/src/Tree/OutboundRouteEntry.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 Microsoft.AspNetCore.Routing.Template;
 

src/Http/Routing/src/Tree/TreeEnumerator.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;
 using System.Collections.Generic;
 using System.Diagnostics;

src/Http/Routing/src/Tree/TreeRouteBuilder.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/Http/Routing/src/Tree/TreeRouter.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.Text.Encodings.Web;

src/Http/Routing/src/Tree/UrlMatchingNode.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/Http/Routing/src/Tree/UrlMatchingTree.cs

@@ -158,7 +158,7 @@ namespace Microsoft.AspNetCore.Routing.Tree
             current.Matches.Sort((x, y) =>
             {
                 var result = x.Entry.Precedence.CompareTo(y.Entry.Precedence);
-                return result == 0 ? x.Entry.RouteTemplate.TemplateText.CompareTo(y.Entry.RouteTemplate.TemplateText) : result;
+                return result == 0 ? x.Entry.RouteTemplate.TemplateText!.CompareTo(y.Entry.RouteTemplate.TemplateText) : result;
             });
         }