The question makes no sense: "mouse down" is something the user does with the physical mouse device, it cannot be disabled. And if you could disable moving the mouse pointer to any area of the screen,
it would greatly damage the usability of the whole system.
It would be hard to invent more irritating system abuse.
However, if you really want, you can "capture" the mouse by some UI element, to dispatch all software mouse events to this element. Please see:
https://msdn.microsoft.com/en-us/library/system.windows.uielement.capturemouse%28v=vs.110%29.aspx[
^],
https://msdn.microsoft.com/en-us/library/system.windows.input.mouse.capture%28v=vs.110%29.aspx[
^],
https://msdn.microsoft.com/en-us/library/system.windows.input.capturemode%28v=vs.110%29.aspx[
^].
But such things should only be done on temporary basis, for relatively short time. Here is one typical application: you want to create button-like behavior of some element. Say, you fist handle
MouseDown on this element and change its state, and, say, it's view. Then you may want to handle
MouseUp to get to the main state of the element, even if by that time the mouse pointer moved away from the element. Then you capture mouse in your
MouseDown and un-capture after you handle
MouseUp. You can use this idea
instead of that hypothetical pointless "disable" action.
—SA
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