Windows Phone Back KeyPress + MessageBox crashes the app without Selection

Question

I have a strange issue overriding BackkeyPress Function in code behind, inside the function i have a simple message box to Go back or cancel navigation ( stay in current page ), when no choice is made (ok or cancel ) and Messagebox is open for long time, Application crashes, when i try to debug, no exception is thrown and App remains in the state unless OK or cancel is pressed , but on Normal run ( without debugger ) the crash is apparent.

    protected override void OnBackKeyPress(System.ComponentModel.CancelEventArgs e)
    {

        string caption = "exit?";
        string message = "Do you still want to exit?";
        e.Cancel = MessageBoxResult.Cancel == MessageBox.Show(message, caption,           
        MessageBoxButton.OKCancel);

        base.OnBackKeyPress(e);

    }

Answer 1

http://msdn.microsoft.com/en-US/library/windowsphone/develop/jj206947(v=vs.105).aspx

In Windows Phone 8, if you call Show in OnBackKeyPress(CancelEventArgs) or a handler for the BackKeyPress event, the app will exit.

You can work around this by calling Show on a different thread, as described in the following steps. Override BackKeyPress or create a handler for the BackKeyPress event. Set the Cancel to true to cancel the back key press action. Dispatch a method that shows the MessageBox. If the user chooses to leave the app, call Terminate(), otherwise, do nothing.