Logging with ASP.NET Core

This article shows how to use PostSharp Logging and ASP.NET Core logging together.

Writing PostSharp Logging events to ASP.NET Core

To send PostSharp Logging events to the logging system of ASP.NET Core:

1. Add PostSharp logging to your codebase as described in Getting Started with PostSharp Logging.

2. Add the PostSharp.Patterns.Diagnostics.Microsoft package to your startup project.

3. Set up ASP.NET Core logging in your CreateHostBuilder like this:

   public static IHostBuilder CreateHostBuilder(string[] args) =>
   Host.CreateDefaultBuilder(args)
     .ConfigureLogging(loggingBuilder =>
     {
       loggingBuilder.ClearProviders();
       loggingBuilder.AddConsole();
     })
     .ConfigureWebHostDefaults(webBuilder => { webBuilder.UseStartup<Startup>(); });
   

4. In appsettings.json and appsettings.Development.json, reduce the minimum logged LogLevel to Debug. PostSharp outputs most traces at the Debug level:

   {
     "Logging": {
       "LogLevel": {
         "Default": "Debug",
         "Microsoft": "Warning",
         "Microsoft.Hosting.Lifetime": "Information"
       }
     }
   }
   

5. Set MicrosoftLoggingBackend as the default backend in your Main method:

   IHost host = CreateHostBuilder(args).Build();
   var loggerFactory = (ILoggerFactory) host.Services.GetService(typeof(ILoggerFactory));
   LoggingServices.DefaultBackend = new MicrosoftLoggingBackend(loggerFactory);
   host.Run();
   

Any methods annotated with LogAttribute will now emit log messages into ASP.NET Core logging, as in this example:

dbug: WebSite1.Pages.RazorPage1[2]
      RazorPage1.HelloWorld() | Starting.
dbug: WebSite1.Pages.RazorPage1[4]
      RazorPage1.HelloWorld() | Succeeded.

Collecting ASP.NET Core logging events into PostSharp Logging

If your source code already emits log events using the ILogger interface of .NET Core, you can configure PostSharp Logging to collect log events directly emitted by ILogger, so that they are all processed by the same PostSharp backend and logger. One of the benefits is that indentation of manual logging and automatic logging will be synchronized. See Collecting Logs from Other Frameworks for more information.

To collect .NET Core manual logging events into PostSharp:

1. Add the PostSharp.Patterns.Diagnostics.Microsoft package to your startup project.

2. Find your CreateHostBuilder method and add ConfigureLogging. All initialization code will go in there:

   public static IHostBuilder CreateHostBuilder(string[] args) =>
   Host.CreateDefaultBuilder(args)
   .ConfigureLogging(loggingBuilder =>
     {
       // Logging initialization code goes here.
     })
   .ConfigureWebHostDefaults(webBuilder => { webBuilder.UseStartup<Startup>(); });
   

3. Replace that code with the following:

   public static IHostBuilder CreateHostBuilder(string[] args) =>
   Host.CreateDefaultBuilder(args)
   .ConfigureLogging(loggingBuilder =>
     {
       // First, set up your final logging providers. These are the providers,
       // such as console or a log file, where you want the final output of logging to go:
       loggingBuilder.ClearProviders();
       loggingBuilder.AddConsole();
   
       // Next, capture those logging providers in a list and remove them:
       List<ILoggerProvider> loggerProviders =  loggingBuilder.Services.BuildServiceProvider().GetServices<ILoggerProvider>().ToList();
       loggingBuilder.ClearProviders();
   
       // Next, add the PostSharp logging provider which sends all events to PostSharp:
       loggingBuilder.AddPostSharp();
   
       // Finally, use the captured providers to create a PostSharp backend and set it as the default backend:
       LoggingServices.DefaultBackend = new MicrosoftLoggingBackend(new LoggerFactory(loggerProviders));
     })
   .ConfigureWebHostDefaults(webBuilder => { webBuilder.UseStartup<Startup>(); });
   

Now, you can use LogAttribute to add automatic logging and Microsoft.Extensions.Logging.ILogger loggers to add manual log messages.

See Also

Reference

MicrosoftLoggingBackend
MicrosoftLoggingCollectingLoggerProvider
Other Resources

Collecting Logs from Other Frameworks