function _nFMouseDown(sender, eventArgs) {
    if (sender.CaptureMouse()) {
        _nFDrag = true;
        _nFOffset = eventArgs.getPosition(sender.GetParent());
    }
}
function _nFMouseUp(sender, eventArgs) {
    if (_nFDrag) {
        sender.ReleaseMouseCapture();
        _nFDrag = false;
    }
}
function _nFMouseMove(sender, eventArgs) {
    if (_nFDrag) {
        var position = eventArgs.getPosition(sender.GetParent().GetParent());
        
        sender.GetParent()["Canvas.Left"] = position.X - _nFOffset.X;
        sender.GetParent()["Canvas.Top"] = position.Y - _nFOffset.Y;
        
    }
}