Difference between delegate.BeginInvoke and using ThreadPool threads in C#

Question

In C# is there any difference between using a delegate to do some work asynchronously (calling BeginInvoke()) and using a ThreadPool thread as shown below

public void asynchronousWork(object num)     {         //asynchronous work to be done         Console.WriteLine(num);     }   public void test()     {         Action<object> myCustomDelegate = this.asynchronousWork;         int x = 7;          //Using Delegate         myCustomDelegate.BeginInvoke(7, null, null);          //Using Threadpool         ThreadPool.QueueUserWorkItem(new WaitCallback(asynchronousWork), 7);         Thread.Sleep(2000);     } 

Edit:
BeginInvoke makes sure that a thread from the thread pool is used to execute the asynchronous code , so is there any difference?

Answer 1

Joe Duffy, in his Concurrent Programming on Windows book (page 418), says this about Delegate.BeginInvoke:

All delegate types, by convention offer a BeginInvoke and EndInvoke method alongside the ordinary synchronous Invoke method. While this is a nice programming model feature, you should stay away from them wherever possible. The implementation uses remoting infrastructure which imposes a sizable overhead to asynchronous invocation. Queue work to the thread pool directly is often a better approach, though that means you have to co-ordinate the rendezvous logic yourself.

EDIT: I created the following simple test of the relative overheads:

int counter = 0; int iterations = 1000000; Action d = () => { Interlocked.Increment(ref counter); };  var stopwatch = new System.Diagnostics.Stopwatch(); stopwatch.Start(); for (int i = 0; i < iterations; i++) {     var asyncResult = d.BeginInvoke(null, null); }  do { } while(counter < iterations); stopwatch.Stop();  Console.WriteLine("Took {0}ms", stopwatch.ElapsedMilliseconds); Console.ReadLine(); 

On my machine the above test runs in around 20 seconds. Replacing the BeginInvoke call with

System.Threading.ThreadPool.QueueUserWorkItem(state => {     Interlocked.Increment(ref counter); }); 

changes the running time to 864ms.