Delegating a task in and getting notified when it completes (in C#)

Question

Conceptually, I would like to accomplish the following but have had trouble understand how to code it properly in C#:

SomeMethod { // Member of AClass{}
    DoSomething;
    Start WorkerMethod() from BClass in another thread;
    DoSomethingElse;
}

Then, when WorkerMethod() is complete, run this:

void SomeOtherMethod()  // Also member of AClass{}
{ ... }

Can anyone please give an example of that?

Answer 1

The BackgroundWorker class was added to .NET 2.0 for this exact purpose.

In a nutshell you do:

BackgroundWorker worker = new BackgroundWorker();
worker.DoWork += delegate { myBClass.DoHardWork(); }
worker.RunWorkerCompleted += new RunWorkerCompletedEventHandler(SomeOtherMethod);
worker.RunWorkerAsync();

You can also add fancy stuff like cancellation and progress reporting if you want :)

Answer 2

In .Net 2 the BackgroundWorker was introduced, this makes running async operations really easy:

BackgroundWorker bw = new BackgroundWorker { WorkerReportsProgress = true };

bw.DoWork += (sender, e) => 
   {
       //what happens here must not touch the form
       //as it's in a different thread
   };

bw.ProgressChanged += ( sender, e ) =>
   {
       //update progress bars here
   };

bw.RunWorkerCompleted += (sender, e) => 
   {
       //now you're back in the UI thread you can update the form
       //remember to dispose of bw now
   };

worker.RunWorkerAsync();

In .Net 1 you have to use threads.