Silverlight click event registered a second time before first event completed

Question

I have a button which launches a "modal dialog" - it just creates a transparent grid covering everything, with the "dialog" created on top of that.

However I have a strange issue - if I double/triple click the button really fast (or add some delay in the event code), the button click event is executed multiple times, creating multiple overlapping modal dialogs. If the first action in my event is to disable the button (IsEnabled=false) it seems to prevent this.

My guess is that Silverlight is being multithreaded with input - it is not only recording the second click in another thread (while the button's click event is running), but it is jumping the gun by evaluating which control should be the target before the previous event has finished executing. Even though that event alters what control is at those mouse coordinates, it doesn't matter.

Does anyone know anything about this behavoir, or a way around it? If I have something like a save window, where the user clicks a save button, a blocking grid ("Saving...") is placed up while it saves, and then the whole "window" is closed, I'd like to avoid the user being able to queue up multiple save event clicks (this could lead to unpredictable program behavoir).

Answer 1

If you've ever worked with WinForms or WPF, this is expected behavior. Your button is broadcasting its Click event until your modal dialog covers it up. Unfortunately, there is some amount of time between your first click and when the modal dialog covers the button which allows multiple clicks to the original button.

You have two solution choices:

1. Disable the button after the first click and then re-enable after the modal dialog returns. You've already mentioned that this works.

2. Write code in the Event Handler of the button to determine if a modal dialog is already being displayed. This way, you're putting the responsibility in one location rather than splitting it up (disabling and re-enabling the button). This would be my preferred solution.

Answer 2

I think what you're seeing is the behaviour of Silverlight's routed events.

You can set the Handled property of the event arguments to true to prevent the event from bubbling.