Merge pull request #1 from GoldenCrystal/dev

Add an overload to UseSerilog() for inline initialization during program startup

Author: nblumhardt

README.md

@@ -88,3 +88,42 @@ Tip: to see Serilog output in the Visual Studio output window when running under
 With _Serilog.AspNetCore_ installed and configured, you can write log messages directly through Serilog or any `ILogger` interface injected by ASP.NET. All loggers will use the same underlying implementation, levels, and destinations.
 
 **Tip:** change the minimum level for `Microsoft` to `Warning` and plug in this [custom logging middleware](https://github.com/datalust/serilog-middleware-example/blob/master/src/Datalust.SerilogMiddlewareExample/Diagnostics/SerilogMiddleware.cs) to clean up request logging output and record more context around errors and exceptions.
+
+### Alternative configuration
+
+You can chose to build the logger as part of the `WebHostBuilder` pipeline, and thus benefit from the application configuration.
+The following code shows an example of such a configuration:
+
+````csharp
+public class Program
+{
+    public static void Main(string[] args)
+    {
+        var host = new WebHostBuilder()
+            .UseKestrel()
+            .UseContentRoot(Directory.GetCurrentDirectory())
+            // Load the application configuration over the web host configuration.
+            .ConfigureAppConfiguration((hostingContext, configurationBuilder) =>
+            {
+                configurationBuilder
+                    .SetBasePath(hostingContext.HostingEnvironment.ContentRootPath)
+                    .AddJsonFile("appsettings.json", optional: false, reloadOnChange: true)
+                    .AddJsonFile($"appsettings.{hostingContext.HostingEnvironment.EnvironmentName}.json", optional: true, reloadOnChange: true)
+                    .AddEnvironmentVariables();
+            })
+            // Configure Serilog to be used as the logger for the whole application.
+            .UseSerilog((hostingContext, loggerConfiguration) =>
+                loggerConfiguration.ReadFrom.Configuration(hostingContext.Configuration)
+                    .Enrich.FromLogContext()
+                    .WriteTo.Console()
+            )
+            .UseIISIntegration()
+            .UseStartup<Startup>()
+            .Build();
+
+        host.Run();
+    }
+}
+````
+
+With this code, the default behavior is to set the created `ILogger` as the default logger. `Log.Logger` can be used as usual to access the created logger.

serilog-aspnetcore.sln

@@ -1,7 +1,7 @@
 
 Microsoft Visual Studio Solution File, Format Version 12.00
 # Visual Studio 15
-VisualStudioVersion = 15.0.26730.10
+VisualStudioVersion = 15.0.26730.12
 MinimumVisualStudioVersion = 10.0.40219.1
 Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "src", "src", "{A1893BD1-333D-4DFE-A0F0-DDBB2FE526E0}"
 EndProject

src/Serilog.AspNetCore/SerilogWebHostBuilderExtensions.cs

@@ -38,7 +38,40 @@ public static IWebHostBuilder UseSerilog(this IWebHostBuilder builder, Serilog.I
         {
             if (builder == null) throw new ArgumentNullException(nameof(builder));
             builder.ConfigureServices(collection =>
-                collection.AddSingleton<ILoggerFactory>(new SerilogLoggerFactory(logger, dispose)));
+                collection.AddSingleton<ILoggerFactory>(services => new SerilogLoggerFactory(logger, dispose)));
+            return builder;
+        }
+
+        /// <summary>Sets Serilog as the logging provider.</summary>
+        /// <remarks>
+        /// A <see cref="WebHostBuilderContext"/> is supplied so that configuration and hosting information can be used.
+        /// The logger will be shut down when application services are disposed.
+        /// </remarks>
+        /// <param name="builder">The web host builder to configure.</param>
+        /// <param name="configureLogger">The delegate for configuring the <see cref="LoggerConfiguration" /> that will be used to construct a <see cref="Logger" />.</param>
+        /// <param name="preserveStaticLogger">Indicates whether to preserve the value of <see cref="Log.Logger"/>.</param>
+        /// <returns>The web host builder.</returns>
+        public static IWebHostBuilder UseSerilog(this IWebHostBuilder builder, Action<WebHostBuilderContext, LoggerConfiguration> configureLogger, bool preserveStaticLogger = false)
+        {
+            if (builder == null) throw new ArgumentNullException(nameof(builder));
+            if (configureLogger == null) throw new ArgumentNullException(nameof(configureLogger));
+            builder.ConfigureServices((context, collection) =>
+            {
+                var loggerConfiguration = new LoggerConfiguration();
+                configureLogger(context, loggerConfiguration);
+                var logger = loggerConfiguration.CreateLogger();
+                if (preserveStaticLogger)
+                {
+                    collection.AddSingleton<ILoggerFactory>(services => new SerilogLoggerFactory(logger, true));
+                }
+                else 
+                {
+                    // Passing a `null` logger to `SerilogLoggerFactory` results in disposal via
+                    // `Log.CloseAndFlush()`, which additionally replaces the static logger with a no-op.
+                    Log.Logger = logger;
+                    collection.AddSingleton<ILoggerFactory>(services => new SerilogLoggerFactory(null, true));
+                }
+            });
             return builder;
         }
     }