private void txt1_MouseUp(object sender, System.Windows.Forms.MouseEventArgs e)
{
System.Type ty = sender.GetType();
int x = e.x;
                            int y = e.y;
                            if(ty.FullName = "System.Windows.Forms.TextBox")
{
                                  比较看当前点是否在txt1范围内
                            }
}