Point mouseOff;//鼠標移動位置變量
        bool leftFlag;//標記是否為左鍵
        private void Form1_MouseDown(object sender, MouseEventArgs e)
        {
            if (e.Button == MouseButtons.Left)
            {
                mouseOff = new Point(-e.X, -e.Y); //得到變量的值
                leftFlag = true;                  //點擊左鍵按下時標注為true;
            }
        }

        private void Form1_MouseMove(object sender, MouseEventArgs e)
        {
            if (leftFlag)
            {
                Point mouseSet = Control.MousePosition;
                mouseSet.Offset(mouseOff.X, mouseOff.Y);  //設置移動后的位置
                Location = mouseSet;
            }
        }

        private void Form1_MouseUp(object sender, MouseEventArgs e)
        {
            if (leftFlag)
            {
                leftFlag = false;//釋放鼠標后標注為false;
            }
        }