Attach EventId as a structure when present. Fixes #33.

Author: nblumhardt

src/Serilog.Extensions.Logging/Extensions/Logging/EventIdEnricher.cs

@@ -0,0 +1,38 @@
+using System.Collections.Generic;
+using Microsoft.Extensions.Logging;
+using Serilog.Core;
+using Serilog.Events;
+
+namespace Serilog.Extensions.Logging
+{
+    /// <summary>
+    /// Attaches <see cref="EventId"/> properties to events that have them. Uses a more compact format than
+    /// the default destructuring provides (no type tag, default properties omitted).
+    /// </summary>
+    class EventIdEnricher : ILogEventEnricher
+    {
+        readonly EventId _eventId;
+
+        public EventIdEnricher(EventId eventId)
+        {
+            _eventId = eventId;
+        }
+
+        public void Enrich(LogEvent logEvent, ILogEventPropertyFactory propertyFactory)
+        {
+            var properties = new List<LogEventProperty>(2);
+
+            if (_eventId.Id != 0)
+            {
+                properties.Add(new LogEventProperty("Id", new ScalarValue(_eventId.Id)));
+            }
+
+            if (_eventId.Name != null)
+            {
+                properties.Add(new LogEventProperty("Name", new ScalarValue(_eventId.Name)));
+            }
+
+            logEvent.AddOrUpdateProperty(new LogEventProperty("EventId", new StructureValue(properties)));
+        }
+    }
+}

src/Serilog.Extensions.Logging/Extensions/Logging/SerilogLogger.cs

@@ -99,8 +99,8 @@ public void Log<TState>(LogLevel logLevel, EventId eventId, TState state, Except
             if (string.IsNullOrEmpty(messageTemplate))
                 return;
 
-            if (eventId.Id != 0)
-                logger = logger.ForContext("EventId", eventId);
+            if (eventId.Id != 0 || eventId.Name != null)
+                logger = logger.ForContext(new[] { new EventIdEnricher(eventId) });
 
             var parsedTemplate = _messageTemplateParser.Parse(messageTemplate);
             var evt = new LogEvent(DateTimeOffset.Now, level, exception, parsedTemplate, Enumerable.Empty<LogEventProperty>());

test/Serilog.Extensions.Logging.Tests/SerilogLoggerTests.cs

@@ -7,6 +7,7 @@
 using Microsoft.Extensions.Logging;
 using System.Collections.Generic;
 using System.IO;
+using System.Linq;
 using Serilog.Debugging;
 using Xunit;
 
@@ -250,6 +251,24 @@ public void CarriesMessageTemplateProperties()
             Assert.Empty(selfLog.ToString());
         }
 
+        [Fact]
+        public void CarriesEventIdIfNonzero()
+        {
+            var t = SetUp(LogLevel.Trace);
+            var logger = t.Item1;
+            var sink = t.Item2;
+
+            int expected = 42;
+
+            logger.Log(LogLevel.Information, expected, "Test", null, null);
+
+            Assert.Equal(1, sink.Writes.Count);
+
+            var eventId = (StructureValue) sink.Writes[0].Properties["EventId"];
+            var id = (ScalarValue) eventId.Properties.Single(p => p.Name == "Id").Value;
+            Assert.Equal(42, id.Value);
+        }
+
         private class FoodScope : IEnumerable<KeyValuePair<string, object>>
         {
             readonly string _name;