Augment logging documentation for Blazor (#17980)

Author: guardrex

aspnetcore/blazor/handle-errors.md

@@ -5,7 +5,7 @@ description: Discover how ASP.NET Core Blazor how Blazor manages unhandled excep
 monikerRange: '>= aspnetcore-3.1'
 ms.author: riande
 ms.custom: mvc
-ms.date: 03/29/2020
+ms.date: 04/23/2020
 no-loc: [Blazor, SignalR]
 uid: blazor/handle-errors
 ---
@@ -106,6 +106,8 @@ During development, Blazor usually sends the full details of exceptions to the b
 
 You must decide which incidents to log and the level of severity of logged incidents. Hostile users might be able to trigger errors deliberately. For example, don't log an incident from an error where an unknown `ProductId` is supplied in the URL of a component that displays product details. Not all errors should be treated as high-severity incidents for logging.
 
+For more information, see <xref:fundamentals/logging/index#create-logs-in-blazor>.
+
 ## Places where errors may occur
 
 Framework and app code may trigger unhandled exceptions in any of the following locations:

aspnetcore/blazor/hosting-model-configuration.md

@@ -5,7 +5,7 @@ description: Learn about Blazor hosting model configuration, including how to in
 monikerRange: '>= aspnetcore-3.1'
 ms.author: riande
 ms.custom: mvc
-ms.date: 04/16/2020
+ms.date: 04/23/2020
 no-loc: [Blazor, SignalR]
 uid: blazor/hosting-model-configuration
 ---
@@ -129,7 +129,7 @@ For more information on how background updates are handled by PWAs, see <xref:bl
 
 ### Logging
 
-For information on Blazor WebAssembly logging support, see <xref:fundamentals/logging/index#create-logs-in-blazor-webassembly>.
+For information on Blazor WebAssembly logging support, see <xref:fundamentals/logging/index#create-logs-in-blazor>.
 
 ## Blazor Server
 
@@ -247,3 +247,7 @@ To configure the SignalR client in the *Pages/_Host.cshtml* file:
   });
 </script>
 ```
+
+### Logging
+
+For information on Blazor Server logging support, see <xref:fundamentals/logging/index#create-logs-in-blazor>.

aspnetcore/fundamentals/logging/index.md

@@ -5,7 +5,7 @@ description: Learn how to use the logging framework provided by the Microsoft.Ex
 monikerRange: '>= aspnetcore-2.1'
 ms.author: riande
 ms.custom: mvc
-ms.date: 4/17/2020
+ms.date: 4/23/2020
 uid: fundamentals/logging/index
 ---
 # Logging in .NET Core and ASP.NET Core
@@ -159,7 +159,9 @@ 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
+### Create logs in Blazor
+
+#### Blazor WebAssembly
 
 Configure logging in Blazor WebAssembly apps with the `WebAssemblyHostBuilder.Logging` property in `Program.Main`:
 
@@ -176,6 +178,63 @@ 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`.
 
+#### Log in Razor components
+
+Loggers respect app startup configuration.
+
+The `using` directive for <xref:Microsoft.Extensions.Logging> is required to support Intellisense completions for APIs, such as <xref:Microsoft.Extensions.Logging.LoggerExtensions.LogWarning%2A> and <xref:Microsoft.Extensions.Logging.LoggerExtensions.LogError%2A>.
+
+The following example demonstrates logging with an <xref:Microsoft.Extensions.Logging.ILogger> in Razor components:
+
+```razor
+@page "/counter"
+@using Microsoft.Extensions.Logging;
+@inject ILogger<Counter> logger;
+
+<h1>Counter</h1>
+
+<p>Current count: @currentCount</p>
+
+<button class="btn btn-primary" @onclick="IncrementCount">Click me</button>
+
+@code {
+    private int currentCount = 0;
+
+    private void IncrementCount()
+    {
+        logger.LogWarning("Someone has clicked me!");
+
+        currentCount++;
+    }
+}
+```
+
+The following example demonstrates logging with an <xref:Microsoft.Extensions.Logging.ILoggerFactory> in Razor components:
+
+```razor
+@page "/counter"
+@using Microsoft.Extensions.Logging;
+@inject ILoggerFactory LoggerFactory
+
+<h1>Counter</h1>
+
+<p>Current count: @currentCount</p>
+
+<button class="btn btn-primary" @onclick="IncrementCount">Click me</button>
+
+@code {
+    private int currentCount = 0;
+
+    private void IncrementCount()
+    {
+        var logger = LoggerFactory.CreateLogger<Counter>();
+        logger.LogWarning("Someone has clicked me!");
+
+        currentCount++;
+    }
+}
+```
+
 ### 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.