Question

I am using Reactive Extensions to verification of a textbox input.
I am trying to use the .Throttle(TimeSpan.FromMilliseconds(500)).

But when I add the .Throttle() method a cross thread exception is thrown when accessing a UI object in the .Subscribe() method.

It works 100% without the Throttle, why is it breaking?

My code:

 var textChangedEvent = Observable.FromEvent<TextChangedEventArgs>(usernameTextbox, "TextChanged")
                                    .Throttle(TimeSpan.FromMilliseconds(500))

        textChangedEvent.Subscribe(changed =>
            {
                TextBox oUsernameTextBox = changed.Sender as TextBox;

                //Accessing oUsernameTextBox throws Cross Thread Exception
            });

Thanks
-Oliver

Answer 1

By default Throttle uses the ThreadpoolScheduler so events will not arrive on the UI Thread. Since you need the events on the UI thread use:-

var textChangedEvent = Observable.FromEvent<TextChangedEventArgs>(usernameTextbox, "TextChanged")
        .Throttle(TimeSpan.FromMilliseconds(500), Scheduler.Dispatcher);

This will put the events back on the UI Thread.