c# 判斷事件中鼠標的左右按鍵

        //定義鼠標的MouseDown事件
        this.MouseDown += new MouseEventHandler(pic_MouseDown);

        void pic_MouseDown(object sender, MouseEventArgs e)
        {
            //判斷是否是右鍵
            if (e.Button==MouseButtons.Right)
            {
                if (this.Image == null)
                {
                    //右鍵[2]不可用
                    gmnPic.Items[2].Enabled = false;             
                }
                else
                {
                    gmnPic.Items[2].Enabled = true;
                }
            }
        }