Question

There are several events which deal with manipulation (and thus drag&drop):

• ManipulationStarting
• ManipulationStarted
• ManipulationDelta
• ManipulationInertiaStarting
• ManipulationCompleted

In the ManipulationStarting event, the event args (type ManipulationStartingRoutedEventArgs) allow me to set the Mode attribute to ManipulationModes.None — is it correct that this means that no manipulation is allowed and thus no drag&drop?

I’m asking because I’ve come across a strange behaviour when I was playing with the official XAML user input events sample application, especially with scenario 4 (drag&drop).

Just set the Mode to ManipulationModes.None in the ManipulationStarting event of Scenario4.xaml.cs:

void ManipulateMe_ManipulationStarting(object sender, ManipulationStartingRoutedEventArgs e)
{
    forceManipulationsToEnd = false;
    e.Mode = ManipulationModes.None;   // <-- this is new
    e.Handled = true;
}

Nevertheless, with every third drag attempt I can drag the rectangle around. I’ve recorded a video to demonstrate this: http://www.youtube.com/watch?v=psytuTailHg.

This problem does not only occur with this sample but also in my own application.

Questions:

• Why is there such a strange behavior?
• What’s the best way to cancel the drag&drop event (for instance if some conditions are not met)?

Answer 1

On a gridview for example you can implement the DragItemStarting event, and set e.Cancel = true; to prevent this behaviour – does that not meet your needs?