Question

I know that Asycronous Delegates are used for implementing Call back functionality in .NET.

I want to know

1. Is it possible to use Callback using ThreadPool?
2. Can I use as many BackgroundWorkers as possible? What I exactly want to know is, Is there any additional overhead involved in using BackgroundWorker instead of ThreadPool/AsyncDelegates/Thread Class?

Answer 1

In response to your first question (if I understood correctly), the answer is yes: I think you are looking for the AsyncOperation class, which can handle reporting progress and completed events back to the calling thread using its Post and PostOperationCompleted methods. This is what the BackgroundWorker is doing under the hood.

See: AsyncOperation Class

private AsyncOperation asyncOperation;

public void DoSomethingAsync()
{
    this.asyncOperation = AsyncOperationManager.CreateOperation(null);
    ThreadPool.QueueUserWorkItem(s => this.DoSomethingImpl());
}

private void DoSomethingImpl()
{
    // report progress
    this.asyncOperation.Post(new SendOrPostCallback(...), null);

    // report complete
    this.asyncOperation.PostOperationCompleted(new SendOrPostCallback(...), null);
}