Adding logging event ids

src/Microsoft.AspNet.Session/DistributedSession.cs

@@ -139,7 +139,7 @@ namespace Microsoft.AspNet.Session
                 }
                 else if (!_isNewSessionKey)
                 {
-                    _logger.LogWarning("Accessing expired session {0}", _sessionId);
+                    _logger.AccessingExpiredSession(_sessionId);
                 }
                 _loaded = true;
             }
@@ -152,7 +152,7 @@ namespace Microsoft.AspNet.Session
                 var data = await _cache.GetAsync(_sessionId);
                 if (_logger.IsEnabled(LogLevel.Information) && data == null)
                 {
-                    _logger.LogInformation("Session {0} started", _sessionId);
+                    _logger.SessionStarted(_sessionId);
                 }
                 _isModified = false;
 

src/Microsoft.AspNet.Session/LoggingExtensions.cs

@@ -0,0 +1,45 @@
+// 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;
+
+namespace Microsoft.Extensions.Logging
+{
+    internal static class LoggingExtensions
+    {
+        private static Action<ILogger, Exception> _errorClosingTheSession;
+        private static Action<ILogger, string, Exception> _accessingExpiredSession;
+        private static Action<ILogger, string, Exception> _sessionStarted;
+
+        static LoggingExtensions()
+        {
+            _errorClosingTheSession = LoggerMessage.Define(
+                eventId: 1,
+                logLevel: LogLevel.Error,
+                formatString: "Error closing the session.");
+            _accessingExpiredSession = LoggerMessage.Define<string>(
+                eventId: 2,
+                logLevel: LogLevel.Warning,
+                formatString: "Accessing expired session {SessionId}");
+            _sessionStarted = LoggerMessage.Define<string>(
+                eventId: 3,
+                logLevel: LogLevel.Information,
+                formatString: "Session {SessionId} started");
+        }
+
+        public static void ErrorClosingTheSession(this ILogger logger, Exception exception)
+        {
+            _errorClosingTheSession(logger, exception);
+        }
+
+        public static void AccessingExpiredSession(this ILogger logger, string sessionId)
+        {
+            _accessingExpiredSession(logger, sessionId, null);
+        }
+
+        public static void SessionStarted(this ILogger logger, string sessionId)
+        {
+            _sessionStarted(logger, sessionId, null);
+        }
+    }
+}

src/Microsoft.AspNet.Session/SessionMiddleware.cs

@@ -106,7 +106,7 @@ namespace Microsoft.AspNet.Session
                     }
                     catch (Exception ex)
                     {
-                        _logger.LogError("Error closing the session.", ex);
+                        _logger.ErrorClosingTheSession(ex);
                     }
                 }
             }