private void ContentGrid_PointerPressed(object sender, PointerRoutedEventArgs e)
{
var pointer = e.GetCurrentPoint(ContentGrid);
//if (pointer.Properties.IsRightButtonPressed)
//{
isDraggingSelection = true;
pressedPos = e.GetCurrentPoint((FrameworkElement)sender);
ContentGrid.CapturePointer(e.Pointer);
Canvas.SetLeft(SelectionRect, pressedPos.Position.X);
Canvas.SetTop(SelectionRect, pressedPos.Position.Y);
//}
}