void Start()
    {
        FrameworkElement root = noesis_view.Content;
        Button btn = (Button)root.FindName("Button_Main");

        //does not fire
        btn.MouseLeftButtonUp += Btn_MouseLeftButtonUp;
        btn.MouseUp += Btn_MouseUp;
        btn.MouseDown += Btn_MouseDown;

        //does fire
        btn.Click += Btn_Click;
        btn.MouseEnter += Btn_MouseEnter;
        btn.MouseDoubleClick += Btn_MouseDoubleClick;
    }
        private void Btn_MouseDown(object sender, MouseButtonEventArgs args)
    {
        Debug.Log("Btn_MouseDown!!!!");
    }

    private void Btn_Click(object sender, RoutedEventArgs args)
    {
        Debug.Log("Btn_Click!!!!");
    }
    

PreviewMouseLeftButtonDown
PreviewMouseDown
PreviewMouseLeftButtonUp
PreviewMouseUp
Click