Serilog.AspNetCore

Serilog logging for ASP.NET Core. This package routes ASP.NET Core log messages through Serilog, so you can get information about ASP.NET's internal operations logged to the same Serilog sinks as your application events.

Instructions

First, install the Serilog.AspNetCore NuGet package into your app. You will need a way to view the log messages - Serilog.Sinks.Console writes these to the console; there are many more sinks available on NuGet.

Install-Package Serilog.AspNetCore -DependencyVersion Highest
Install-Package Serilog.Sinks.Console

Next, in your application's Program.cs file, configure Serilog first. A try/catch block will ensure any configuration issues are appropriately logged:

public class Program
{
    public static int Main(string[] args)
    {
        Log.Logger = new LoggerConfiguration()
            .MinimumLevel.Debug()
            .MinimumLevel.Override("Microsoft", LogEventLevel.Information)
            .Enrich.FromLogContext()
            .WriteTo.Console()
            .CreateLogger();

        try
        {
            Log.Information("Starting web host");
            BuildWebHost(args).Run();
            return 0;
        }
        catch (Exception ex)
        {
            Log.Fatal(ex, "Host terminated unexpectedly");
            return 1;
        }
        finally
        {
            Log.CloseAndFlush();
        }
    }

Then, add UseSerilog() to the web host builder in BuildWebHost().

    public static IWebHost BuildWebHost(string[] args) =>
        WebHost.CreateDefaultBuilder(args)
	    .UseStartup<Startup>()
            .UseSerilog() // <-- Add this line
            .Build();
}

Finally, clean up by removing the remaining configuration for the default logger:

Remove calls to AddLogging()
Remove the "Logging" section from appsettings.json files (this can be replaced with Serilog configuration as shown in this example, if required)
Remove ILoggerFactory parameters and any Add*() calls on the logger factory in Startup.cs
Remove UseApplicationInsights() (this can be replaced with the Serilog AI sink, if required)

That's it! With the level bumped up a little you will see log output like:

[22:14:44.646 DBG] RouteCollection.RouteAsync
	Routes: 
		Microsoft.AspNet.Mvc.Routing.AttributeRoute
		{controller=Home}/{action=Index}/{id?}
	Handled? True
[22:14:44.647 DBG] RouterMiddleware.Invoke
	Handled? True
[22:14:45.706 DBG] /lib/jquery/jquery.js not modified
[22:14:45.706 DBG] /css/site.css not modified
[22:14:45.741 DBG] Handled. Status code: 304 File: /css/site.css

Tip: to see Serilog output in the Visual Studio output window when running under IIS, select ASP.NET Core Web Server from the Show output from drop-down list.

A more complete example, showing appsettings.json configuration, can be found in the sample project here.

Using the package

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 to clean up request logging output and record more context around errors and exceptions.

Inline initialization

You can alternatively configure Serilog using a delegate as shown below:

    // dotnet add package Serilog.Settings.Configuration
    .UseSerilog((hostingContext, loggerConfiguration) => loggerConfiguration
	.ReadFrom.Configuration(hostingContext.Configuration)
	.Enrich.FromLogContext()
	.WriteTo.Console())

This has the advantage of making the hostingContext's Configuration object available for configuration of the logger, but at the expense of recording Exceptions raised earlier in program startup.

If this method is used, Log.Logger is assigned implicitly, and closed when the app is shut down.

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