[Preview 4] Logging configuration in Blazor WASM (#17671)

Author: guardrex

aspnetcore/blazor/hosting-model-configuration.md

@@ -127,6 +127,10 @@ Configuration files are cached for offline use. With [Progressive Web Applicatio
 
 For more information on how background updates are handled by PWAs, see <xref:blazor/progressive-web-app#background-updates>.
 
+### Logging
+
+For information on Blazor WebAssembly logging support, see <xref:fundamentals/logging/index#create-logs-in-blazor-webassembly>.
+
 ## Blazor Server
 
 ### Reflect the connection state in the UI

aspnetcore/fundamentals/logging/index.md

@@ -159,6 +159,23 @@ If you need to configure a service that depends on `ILogger<T>`, you can still d
 
 The preceding highlighted code is a `Func` that runs the first time the DI container needs to construct an instance of `MyService`. You can access any of the registered services in this way.
 
+### Create logs in Blazor WebAssembly
+
+Configure logging in Blazor WebAssembly apps with the `WebAssemblyHostBuilder.Logging` property in `Program.Main`:
+
+```csharp
+using Microsoft.AspNetCore.Components.WebAssembly.Hosting;
+
+...
+
+var builder = WebAssemblyHostBuilder.CreateDefault(args);
+
+builder.Logging.SetMinimumLevel(LogLevel.Debug);
+builder.Logging.AddProvider(new CustomLoggingProvider());
+```
+
+The `Logging` property is of type <xref:Microsoft.Extensions.Logging.ILoggingBuilder>, so all of the extension methods available on <xref:Microsoft.Extensions.Logging.ILoggingBuilder> are also available on `Logging`.
+
 ### No asynchronous logger methods
 
 Logging should be so fast that it isn't worth the performance cost of asynchronous code. If your logging data store is slow, don't write to it directly. Consider writing the log messages to a fast store initially, then move them to the slow store later. For example, if you're logging to SQL Server, you don't want to do that directly in a `Log` method, since the `Log` methods are synchronous. Instead, synchronously add log messages to an in-memory queue and have a background worker pull the messages out of the queue to do the asynchronous work of pushing data to SQL Server. For more information, see [this](https://github.com/dotnet/AspNetCore.Docs/issues/11801) GitHub issue.