/// <summary>
///     Attach this behaviour to any framework element to allow the entire parent window to be moved
///     when you click and drag this element.
/// </summary>
public class DragWindowBehaviour : Behavior<FrameworkElement>
{
    private Window _parentWindow;
 
    protected override void OnAttached()
    {
        _parentWindow = GetParentWindow(AssociatedObject);
        if (_parentWindow == null) return;
        AssociatedObject.PreviewMouseLeftButtonDown += _associatedObject_MouseLeftButtonDown;
    }
 
    private void _associatedObject_MouseLeftButtonDown(object sender, MouseButtonEventArgs e)
    {
        _parentWindow.DragMove();
    }
 
    private static Window GetParentWindow(DependencyObject attachedElement)
    {
        return attachedElement.TryFindParent<Window>();
    }
 
    protected override void OnDetaching()
    {
        AssociatedObject.PreviewMouseLeftButtonDown -= _associatedObject_MouseLeftButtonDown;
        _parentWindow = null;
    }
}