EventLog Scopes (#741)

Author: pakrym

src/Microsoft.Extensions.Logging.EventLog/EventLogLogger.cs

@@ -15,6 +15,8 @@ public class EventLogLogger : ILogger
     {
         private readonly string _name;
         private readonly EventLogSettings _settings;
+        private readonly IExternalScopeProvider _externalScopeProvider;
+
         private const string ContinuationString = "...";
         private readonly int _beginOrEndMessageSegmentSize;
         private readonly int _intermediateMessageSegmentSize;
@@ -34,9 +36,22 @@ public EventLogLogger(string name)
         /// <param name="name">The name of the logger.</param>
         /// <param name="settings">The <see cref="EventLogSettings"/>.</param>
         public EventLogLogger(string name, EventLogSettings settings)
+            : this(name, settings, new LoggerExternalScopeProvider())
+        {
+
+        }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="EventLogLogger"/> class.
+        /// </summary>
+        /// <param name="name">The name of the logger.</param>
+        /// <param name="settings">The <see cref="EventLogSettings"/>.</param>
+        /// <param name="externalScopeProvider">The <see cref="IExternalScopeProvider"/>.</param>
+        public EventLogLogger(string name, EventLogSettings settings, IExternalScopeProvider externalScopeProvider)
         {
             _name = string.IsNullOrEmpty(name) ? nameof(EventLogLogger) : name;
             _settings = settings;
+            _externalScopeProvider = externalScopeProvider;
 
             var logName = string.IsNullOrEmpty(settings.LogName) ? "Application" : settings.LogName;
             var sourceName = string.IsNullOrEmpty(settings.SourceName) ? "Application" : settings.SourceName;
@@ -63,7 +78,7 @@ public EventLogLogger(string name, EventLogSettings settings)
         /// <inheritdoc />
         public IDisposable BeginScope<TState>(TState state)
         {
-            return NoopDisposable.Instance;
+            return _externalScopeProvider?.Push(state);
         }
 
         /// <inheritdoc />
@@ -102,9 +117,11 @@ public void Log<TState>(
 
             if (exception != null)
             {
-                message += Environment.NewLine + Environment.NewLine + exception.ToString();
+                message += Environment.NewLine + Environment.NewLine + exception;
             }
 
+            _externalScopeProvider?.ForEachScope<object>((scope, _) => message += Environment.NewLine + scope, null);
+
             WriteMessage(message, GetEventLogEntryType(logLevel), eventId.Id);
         }
 

src/Microsoft.Extensions.Logging.EventLog/EventLogLoggerProvider.cs

@@ -9,10 +9,12 @@ namespace Microsoft.Extensions.Logging.EventLog
     /// The provider for the <see cref="EventLogLogger"/>.
     /// </summary>
     [ProviderAlias("EventLog")]
-    public class EventLogLoggerProvider : ILoggerProvider
+    public class EventLogLoggerProvider : ILoggerProvider, ISupportExternalScope
     {
         private readonly EventLogSettings _settings;
 
+        private IExternalScopeProvider _scopeProvider;
+
         /// <summary>
         /// Initializes a new instance of the <see cref="EventLogLoggerProvider"/> class.
         /// </summary>
@@ -39,5 +41,10 @@ public ILogger CreateLogger(string name)
         public void Dispose()
         {
         }
+
+        public void SetScopeProvider(IExternalScopeProvider scopeProvider)
+        {
+            _scopeProvider = scopeProvider;
+        }
     }
 }

test/Microsoft.Extensions.Logging.Test/EventLogLoggerTest.cs

@@ -120,6 +120,32 @@ public void MessageWithinMaxSize_WritesFullMessage(int messageSize)
             Assert.Equal(expectedMessage, testEventLog.Messages[0]);
         }
 
+
+        [Fact]
+        public void Message_WritesFullMessageWithScopes()
+        {
+            // Arrange
+            var loggerName = "Test";
+            var maxMessageSize = 50 + loggerName.Length + Environment.NewLine.Length;
+            var expectedMessage = loggerName + Environment.NewLine +
+                                  "Message" + Environment.NewLine +
+                                  "Outer Scope" + Environment.NewLine +
+                                  "Inner Scope";
+            var testEventLog = new TestEventLog(maxMessageSize);
+            var logger = new EventLogLogger(loggerName, new EventLogSettings() { EventLog = testEventLog });
+
+            // Act
+            using (logger.BeginScope("Outer Scope"))
+            using (logger.BeginScope("Inner Scope"))
+            {
+                logger.LogInformation("Message");
+            }
+
+            // Assert
+            Assert.Single(testEventLog.Messages);
+            Assert.Equal(expectedMessage, testEventLog.Messages[0]);
+        }
+
         public static TheoryData<int, string[]> WritesSplitMessagesData
         {
             get