.NET Can I wait for a specific background thread finish, then another background thread starts?

Question

thank you for the asnwers

Answer 1

Yes.

And if you provide more information, we can provide more detail in the answer.

In general, you set up a communication system (a message queue, Event, or delegate) that is used to signal that a process/step/thread is done. When that happens, start up the next thread.

Answer 2

Sure. Have the first thread launch the second thread, or set some sort of flag telling the hosting app to start the second thread. Of course, I have to ask: if these threads always run sequentially, why create a second thread at all instead of performing all of your work in the first thread?

Answer 3

In .NET 4, you can use Task instead of threads, and then use continuations to achieve your goals:

var firstTask = Task.Factory.StartNew( () => PerformSomeLongRunningAction(); );

var secondTask = firstTask.ContinueWith( t => PerformSecondAction(); );

In .NET <=3.5, the options vary. The best is often to use a WaitHandle to signal your second task. The first background thread will need to signal the wait handle when it's complete:

var mre = new ManualResetEvent(false);

ThreadPool.QueueUserWorkItem( o =>
      {
           PerformSomeLongRunningAction();
           mre.Set(); // Signal to second thread that it can continue
      });

ThreadPool.QueueUserWorkItem( o =>
      {
           mre.WaitOne(); // Wait for first thread to finish
           PerformSecondAction();
      });