C＃WPF多线程无法从VS2013中的Dispatcher.BeginInvoke返回实际值

Question

I would like to get the return value from a thread in C# VS2013 WPF.

The code is:

int t = 0;
Application.Current.Dispatcher.BeginInvoke(DispatcherPriority.Normal, new Action(() =>
    t = myFucntion(myObject) // if I do not use dispatcher, myObject cannot be accessed by the calling thread. 
));
return t;

Why t is always 0 and not return the actual value ? The solution here does not work for me.

WPF Dispatcher Invoke return value is always null

UPDATE

Application.Current.Dispatcher.Invoke((() =>
        {
          t = myFunction(myObject));
        }));
return t;

But, t is not assigned to the actual value returned from myFunction.

Answer 1

Dispatcher.BeginInvoke is asynchronous. It will return immediatly after queuing the delegate to the message loop:

Executes the specified delegate asynchronously at the specified priority on the thread the Dispatcher is associated with.

That means that you have a race-condition, and you might even see t actually contain the expected value if you run it enough times.

To eliminate that, If you want to wait until the delegate is ran on the message loop, use Dispatcher.Invoke instead:

Application.Current.Dispatcher.Invoke(DispatcherPriority.Normal, 
                                      new Action(() => t = myFunction()));