Synchronize dispatcher and caller

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Posted on Monday August 2013

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More Windows Phone/Silverlight/WPF/(and probably WinRT) goodness.

Sometimes you want to know that any work pushed to the UI dispatcher has completed. For awhile I worked with the idea that Thread.Sleep(1) would let any pending work complete. It doesn't.

A much better approach is to use some thread signalling. The calling thread will wait until the dispatched work has completed, or give up after some period.

        private static void WaitWithDispatcher(Action action)
        {
            if (Deployment.Current.Dispatcher.CheckAccess())
            {
                action();
                return;
            }

            var wait = new AutoResetEvent(false);

            Deployment.Current.Dispatcher.BeginInvoke(() =>
            {
                try
                {
                    action();
                }
                finally
                {
                    // always signal so code can continue
                    wait.Set();
                }
            });

            // wait for a reasonable period for dispatcher to complete
            wait.WaitOne(TimeSpan.FromSeconds(10));
        }

        private static void WithDispatcher(Action action)
        {
            if (Deployment.Current.Dispatcher.CheckAccess())
            {
                action();
                return;
            }

            Deployment.Current.Dispatcher.BeginInvoke(action);
        }