Use LogEvent.UnstableAssembleFromParts() to avoid a dictionary alloc

Author: nblumhardt

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

@@ -93,30 +93,30 @@ LogEvent PrepareWrite<TState>(LogEventLevel level, EventId eventId, TState state
     {
         string? messageTemplate = null;
 
-        var properties = new List<LogEventProperty>();
+        var properties = new Dictionary<string, LogEventPropertyValue>();
 
         if (state is IEnumerable<KeyValuePair<string, object>> structure)
         {
             foreach (var property in structure)
             {
-                if (property.Key == SerilogLoggerProvider.OriginalFormatPropertyName && property.Value is string value)
+                if (property is { Key: SerilogLoggerProvider.OriginalFormatPropertyName, Value: string value })
                 {
                     messageTemplate = value;
                 }
                 else if (property.Key.StartsWith("@"))
                 {
                     if (_logger.BindProperty(GetKeyWithoutFirstSymbol(DestructureDictionary, property.Key), property.Value, true, out var destructured))
-                        properties.Add(destructured);
+                        properties.Add(destructured.Name, destructured.Value);
                 }
                 else if (property.Key.StartsWith("$"))
                 {
                     if (_logger.BindProperty(GetKeyWithoutFirstSymbol(StringifyDictionary, property.Key), property.Value?.ToString(), true, out var stringified))
-                        properties.Add(stringified);
+                        properties.Add(stringified.Name, stringified.Value);
                 }
                 else
                 {
                     if (_logger.BindProperty(property.Key, property.Value, false, out var bound))
-                        properties.Add(bound);
+                        properties.Add(bound.Name, bound.Value);
                 }
             }
 
@@ -127,7 +127,7 @@ LogEvent PrepareWrite<TState>(LogEventLevel level, EventId eventId, TState state
             {
                 messageTemplate = "{" + stateType.Name + ":l}";
                 if (_logger.BindProperty(stateType.Name, AsLoggableValue(state, formatter), false, out var stateTypeProperty))
-                    properties.Add(stateTypeProperty);
+                    properties.Add(stateTypeProperty.Name, stateTypeProperty.Value);
             }
         }
 
@@ -150,19 +150,19 @@ LogEvent PrepareWrite<TState>(LogEventLevel level, EventId eventId, TState state
             if (propertyName != null)
             {
                 if (_logger.BindProperty(propertyName, AsLoggableValue(state, formatter!), false, out var property))
-                    properties.Add(property);
+                    properties.Add(property.Name, property.Value);
             }
         }
 
         if (eventId.Id != 0 || eventId.Name != null)
-            properties.Add(CreateEventIdProperty(eventId));
+            properties.Add("EventId", CreateEventIdPropertyValue(eventId));
 
         var (traceId, spanId) = Activity.Current is { } activity ?
             (activity.TraceId, activity.SpanId) :
             (default(ActivityTraceId), default(ActivitySpanId));
 
         var parsedTemplate = MessageTemplateParser.Parse(messageTemplate ?? "");
-        return new LogEvent(DateTimeOffset.Now, level, exception, parsedTemplate, properties, traceId, spanId);
+        return LogEvent.UnstableAssembleFromParts(DateTimeOffset.Now, level, exception, parsedTemplate, properties, traceId, spanId);
     }
 
     static object? AsLoggableValue<TState>(TState state, Func<TState, Exception?, string>? formatter)
@@ -173,7 +173,7 @@ LogEvent PrepareWrite<TState>(LogEventLevel level, EventId eventId, TState state
         return stateObj ?? state;
     }
 
-    internal static LogEventProperty CreateEventIdProperty(EventId eventId)
+    internal static StructureValue CreateEventIdPropertyValue(EventId eventId)
     {
         var properties = new List<LogEventProperty>(2);
 
@@ -191,6 +191,6 @@ internal static LogEventProperty CreateEventIdProperty(EventId eventId)
             properties.Add(new LogEventProperty("Name", new ScalarValue(eventId.Name)));
         }
 
-        return new LogEventProperty("EventId", new StructureValue(properties));
+        return new StructureValue(properties);
     }
 }

src/Serilog.Extensions.Logging/Serilog.Extensions.Logging.csproj

@@ -29,7 +29,7 @@
     <None Include="..\..\assets\serilog-extension-nuget.png" Pack="true" PackagePath="" Visible="false" />
     <None Include="..\..\README.md" Pack="true" PackagePath="\" Visible="false" />
     <PackageReference Include="Microsoft.SourceLink.GitHub" Version="1.1.1" PrivateAssets="All" />
-    <PackageReference Include="Serilog" Version="3.1.1" />
+    <PackageReference Include="Serilog" Version="4.0.0-*" />
     <!-- The version of this reference must match the major and minor components of the package version prefix. -->
     <PackageReference Include="Microsoft.Extensions.Logging" Version="8.0.0" />
     <PackageReference Include="Nullable" Version="1.3.1" PrivateAssets="All" />

test/Serilog.Extensions.Logging.Benchmarks/LogEventBenchmark.cs

@@ -25,7 +25,7 @@ namespace Serilog.Extensions.Logging.Benchmarks
     [MemoryDiagnoser]
     public class LogEventBenchmark
     {
-        private class Person
+        class Person
         {
             public string? Name { get; set; }
             public int Age { get; set; }
@@ -58,8 +58,8 @@ public void LogInformation()
         [Benchmark]
         public void LogInformationScoped()
         {
-            using (var scope = _melLogger.BeginScope("Hi {@User} from {$Me}", _bob, _alice))
-                _melLogger.LogInformation("Hi");
+            using var scope = _melLogger.BeginScope("Hi {@User} from {$Me}", _bob, _alice);
+            _melLogger.LogInformation("Hi");
         }
     }
 }

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

@@ -500,9 +500,9 @@ public IDisposable Push(object? state)
             return scope;
         }
 
-        private class Scope : IDisposable
+        class Scope : IDisposable
         {
-            public bool IsDisposed { get; set; } = false;
+            public bool IsDisposed { get; set; }
             public object? Value { get; set; }
 
             public Scope(object? value)
@@ -525,8 +525,7 @@ public void Dispose()
     public void LowAndHighNumberedEventIdsAreMapped(int id)
     {
         var orig = new EventId(id, "test");
-        var mapped = SerilogLogger.CreateEventIdProperty(orig);
-        var value = Assert.IsType<StructureValue>(mapped.Value);
+        var value = SerilogLogger.CreateEventIdPropertyValue(orig);
         Assert.Equal(2, value.Properties.Count);
         var idValue = value.Properties.Single(p => p.Name == "Id").Value;
         var scalar = Assert.IsType<ScalarValue>(idValue);