Invoking a delegate on a thread pool

This recipe will show you how to execute a delegate asynchronously on a thread pool. In addition, we will discuss an approach called the Asynchronous Programming Model (APM), which was historically the first asynchronous programming pattern in .NET.

Getting ready

To step into this recipe, you will need Visual Studio 2015. There are no other prerequisites. The source code for this recipe can be found at BookSamples\Chapter3\Recipe1.

How to do it...

To understand how to invoke a delegate on a thread pool, perform the following steps:

1. Start Visual Studio 2015. Create a new C# console application project.

2. In the Program.cs file, add the following using directives:

   using System;
   using System.Threading;
   using static System.Console;
   using static System.Threading.Thread;

3. Add the following code snippet below the Main method:

   private delegate string RunOnThreadPool(out int threadId);
   
   private static void Callback(IAsyncResult ar)
   {
     WriteLine("Starting a callback..."...