Question

A C#-method is calling on the main-thread after event raising. Then an another event is firing this same method during the first event is busy with the same method. So during debugging, I see in the calling stack two line in the same method on the same thread.

How can I hinder that the second event waits until the first event is ready with the same method. I’m trying with lock() but it doesn’t block the same thread. AutoResetEvent can wait but will be waiting on the same thread.

Somebody has the tip? Thanks.

Answer 1

Your problem is caused by Application.DoEvents(). This method does have its uses but it is dangerous, you stumbled onto one of the reasons : re-entrant calls to events.

So, try

1. remove and avoid DoEvents().
2. or make all your eventhandlers capable of or resistant to re-entrancy. Take a critical look at what scenarios are possible with the close button for instance. A simple trick could be:

private bool busy = false;    
private void MyHandler(sender s, EventArgs e)
{
  if (busy)
    return;   // giving up, no queuing

  busy = true;
  // code
  busy = false;  // maybe in a finally clause
}