C# Avoid creation of thread when entering method the second time

开发者_C百科say we declare and run a thread in a method which has a while(1) loop. How can one avoid to create and run a second thread when the method is called again? I only want one thread to start in this method and every time the method is called again, there should be no thread creation all over again. Should I check for the thread name or should I declare the thread as a field of the class?

Any ideas how to do this?

Thanks, Juergen

It sounds like the thread should indeed be a field of the class - although you'll have to be careful to access it in a thread-safe way, if there could be several threads calling the method to start with.

What do you want to happen the second time - should the method block, or just finish immediately, or perhaps throw an exception? If you don't need to wait for the thread to finish, you might be able to get away with just a flag instead of keeping a reference to the thread itself.

(Note that I've been assuming this is an instance method and you want one extra thread per instance.) If that's not the case, you'll have to adjust accordingly.

Have the method return a singleton, and start the thread in the singleton constructor.

Could you save the synchronization context the first time, check on subsequent times to see if it matches, and post back to it if necessary?

SynchronizationContext syncContext = null;
...

// "object state" is required to be a callback for Post
public void HiThar(object state) { 
  if (syncContext == null) {
    syncContext = SynchronizationContext.Current;
  } else {
    syncContext.Post(HiThar, state);
  }
}