Error in ACM adapter example fixed based on feedback by @rexcfnghk. #4

content/posts/ambient-composition-model.md

@@ -1,12 +1,12 @@
 ---
-title:			"The Ambient Composition Model"
-date:			2019-07-15
-author: 		Steven van Deursen
-reviewers:		Peter Parker and Ric Slappendel
-proofreaders:	Katie Tennant
-tags:			[.NET General, Architecture, C#, Dependency Injection]
-gitHubIssueId:	4
-draft:			false
+title:         "The Ambient Composition Model"
+date:          2019-07-15
+author:        Steven van Deursen
+reviewers:     Peter Parker and Ric Slappendel
+proofreaders:  Katie Tennant
+tags:          [.NET General, Architecture, C#, Dependency Injection]
+gitHubIssueId: 4
+draft:         false
 aliases:
     - /p/acm
 ---
@@ -169,15 +169,20 @@ In this example, `ShoppingBasketRepository` is injected with `AmbientShoppingBas
 // This class will be part of your Composition Root
 class AmbientShoppingBasketContextProvider : IShoppingBasketContextProvider
 {
+    private readonly string connectionString;
     private readonly AsyncLocal<ShoppingBasketDbContext> context;
 
     public AmbientShoppingBasketContextProvider(string connectionString)
     {
-        this.context = new AsyncLocal<ShoppingBasketDbContext>(
-            () => new ShoppingBasketDbContext(connectionString));
+        this.connectionString = connectionString;
+        this.context = new AsyncLocal<ShoppingBasketDbContext>();
     }
 
-    public ShoppingBasketDbContext Context => this.context.Value;
+    public ShoppingBasketDbContext Context =>
+        this.context.Value ?? (this.context.Value = this.CreateNew());
+
+    private ShoppingBasketDbContext CreateNew() =>
+        new ShoppingBasketDbContext(this.connectionString);
 }
 {{< / highlightEx >}}
 

content/posts/di-composition-models-comparison.md

@@ -36,7 +36,7 @@ The ACM is perhaps less known, but not less interesting, and there are some down
 
 I should start with the elephant in the room: there is little reason to try to compare the two composition models when one is technically infeasible in the environment you’re working in. I’ll give an example for each model.
 
-With the introduction of the new asynchronous programming model in .NET 4.0, you can now write code that doesn’t block threads but instead uses the more-efficient I/O completion ports. With this model, it is no longer possible to link ambient data to a specific thread—a single request flows (sequentially) from thread to thread. Instead, different constructs should be used, such as [`AsyncLocal<T>`](https://docs.microsoft.com/en-us/dotnet/api/system.threading.asynclocal-1) and [`CallContext`](https://docs.microsoft.com/en-us/dotnet/api/system.runtime.remoting.messaging.callcontext). They represent “ambient data that is local to a given asynchronous control flow, such as an asynchronous method.” `AsyncLocal<T>`, however, was added to .NET 4.6, while `CallContext` is only available in the full .NET version, and its semantics changed in .NET 4.5 to make it usable in combination with async/await.
+With the introduction of the new asynchronous programming model in .NET 4.0, you can now write code that doesn’t block threads but instead uses the more-efficient I/O completion ports. With this model it is no longer possible to link ambient data to a specific thread—a single request flows (sequentially) from thread to thread. Instead, different constructs should be used, such as [`AsyncLocal<T>`](https://docs.microsoft.com/en-us/dotnet/api/system.threading.asynclocal-1) and [`CallContext`](https://docs.microsoft.com/en-us/dotnet/api/system.runtime.remoting.messaging.callcontext). They represent “ambient data that is local to a given asynchronous control flow, such as an asynchronous method.” `AsyncLocal<T>`, however, was added to .NET 4.6, while `CallContext` is only available in the full .NET version, and its semantics changed in .NET 4.5 to make it usable in combination with async/await.
 
 In the good old days, when working with the asynchronous programming model in old environments such as .NET 4.0 and Silverlight, there were issues regarding the use of ambient data.