Use a Func<T> to get the current config value

docs/core/extensions/custom-logging-provider.md

@@ -3,7 +3,7 @@ title: Implement a custom logging provider in .NET
 description: Learn how to implement a custom logging provider in your .NET applications.
 author: IEvangelist
 ms.author: dapine
-ms.date: 05/06/2021
+ms.date: 06/22/2021
 ms.topic: how-to
 ---
 
@@ -28,13 +28,15 @@ The `ILogger` implementation category name is typically the logging source. For
 The preceding code:
 
 - Creates a logger instance per category name.
-- Checks `_config.LogLevels.ContainsKey(logLevel)` in `IsEnabled`, so each `logLevel` has a unique logger. Loggers should also be enabled for all higher log levels:
+- Checks `_getCurrentConfig().LogLevels.ContainsKey(logLevel)` in `IsEnabled`, so each `logLevel` has a unique logger. Loggers should also be enabled for all higher log levels:
 
 :::code language="csharp" source="snippets/configuration/console-custom-logging/ColorConsoleLogger.cs" range="16-17":::
 
+The logger is instantiated with the `name` and a `Func<ColorConsoleLoggerConfiguration>` which will return the current config &mdash; this handles updates to the config values as monitored through the <xref:Microsoft.Extensions.Options.IOptionsMonitor%601.OnChange%2A?displayProperty=nameWithType> callback.
+
 ## Custom logger provider
 
-The `ILoggerProvider` object is responsible for creating logger instances. Maybe it is not needed to create a logger instance per category, but this makes sense for some loggers, like NLog or log4net. Doing this you are also able to choose different logging output targets per category if needed:
+The `ILoggerProvider` object is responsible for creating logger instances. It's not necessary to create a logger instance per category, but it makes sense for some loggers, like NLog or log4net. This strategy allows you to choose different logging output targets per category, as in the following example:
 
 :::code language="csharp" source="snippets/configuration/console-custom-logging/ColorConsoleLoggerProvider.cs":::
 

docs/core/extensions/snippets/configuration/console-custom-logging/ColorConsoleLogger.cs

@@ -4,17 +4,17 @@
 public class ColorConsoleLogger : ILogger
 {
     private readonly string _name;
-    private readonly ColorConsoleLoggerConfiguration _config;
+    private readonly Func<ColorConsoleLoggerConfiguration> _getCurrentConfig;
 
     public ColorConsoleLogger(
         string name,
-        ColorConsoleLoggerConfiguration config) =>
-        (_name, _config) = (name, config);
+        Func<ColorConsoleLoggerConfiguration> getCurrentConfig) =>
+        (_name, _getCurrentConfig) = (name, getCurrentConfig);
 
     public IDisposable BeginScope<TState>(TState state) => default;
 
     public bool IsEnabled(LogLevel logLevel) =>
-        _config.LogLevels.ContainsKey(logLevel);
+        _getCurrentConfig().LogLevels.ContainsKey(logLevel);
 
     public void Log<TState>(
         LogLevel logLevel,
@@ -28,11 +28,12 @@ public void Log<TState>(
             return;
         }
 
-        if (_config.EventId == 0 || _config.EventId == eventId.Id)
+        ColorConsoleLoggerConfiguration config = _getCurrentConfig();
+        if (config.EventId == 0 || config.EventId == eventId.Id)
         {
             ConsoleColor originalColor = Console.ForegroundColor;
 
-            Console.ForegroundColor = _config.LogLevels[logLevel];
+            Console.ForegroundColor = config.LogLevels[logLevel];
             Console.WriteLine($"[{eventId.Id,2}: {logLevel,-12}]");
 
             Console.ForegroundColor = originalColor;

docs/core/extensions/snippets/configuration/console-custom-logging/ColorConsoleLoggerProvider.cs

@@ -17,7 +17,9 @@ public ColorConsoleLoggerProvider(
     }
 
     public ILogger CreateLogger(string categoryName) =>
-        _loggers.GetOrAdd(categoryName, name => new ColorConsoleLogger(name, _currentConfig));
+        _loggers.GetOrAdd(categoryName, name => new ColorConsoleLogger(name, GetCurrentConfig));
+
+    private ColorConsoleLoggerConfiguration GetCurrentConfig() => _currentConfig;
 
     public void Dispose()
     {