private int GetSlot(PictureBox sender) => SlotPictureBoxes.IndexOf(sender);
private int GetSlot(PictureBox sender) => SlotPictureBoxes.IndexOf(WinFormsUtil.GetUnderlyingControl(sender) as PictureBox);
private int GetSlot(PictureBox sender) => SlotPictureBoxes.IndexOf(sender);
private int GetSlot(PictureBox sender) => SlotPictureBoxes.IndexOf(WinFormsUtil.GetUnderlyingControl(sender) as PictureBox);