【NCRE】C# WindowForm实现屏幕最顶端拖动

   需求：

           窗体置顶，同时显示在任何窗体的最上方，在电脑屏幕上实现左右拖拽。

    代码：

           

<span style="font-size:24px;">        private Point mouseOffset; 　　　　//记录鼠标指针的坐标   
        private bool isMouseDown = false; //记录鼠标按键是否按下
        private bool isBoundary = false;    //是否在边界上
        private void frmxuanfukuang_MouseDown_1(object sender, MouseEventArgs e)
        {
            int xOffset;
            //int yOffset;
            if (e.Button == MouseButtons.Left)
            {
                xOffset = -e.X - SystemInformation.FrameBorderSize.Width;
                //yOffset = -e.Y - SystemInformation.CaptionHeight - SystemInformation.FrameBorderSize.Height;
                mouseOffset = new Point(xOffset, 0);
                //this.MouseMove += frmxuanfukuang_MouseMove;
                isBoundary = false;
                isMouseDown = true;
            }

        }

        private void frmxuanfukuang_MouseMove_1(object sender, MouseEventArgs e)
        {
            Rectangle ScreenArea = System.Windows.Forms.Screen.GetWorkingArea(this);
            int screenWidth = ScreenArea.Width; //屏幕宽度 
            Point mousePos = Control.MousePosition;
            mousePos.Offset(mouseOffset.X, 0);
            if (this.Location.X < 0)
            {
                this.Location = new Point(10, this.Location.Y);
                isMouseDown = false;
            }
            if (this.Location.X + this.Width > screenWidth)
            {
                this.Location = new Point(screenWidth - 10 - this.Width, this.Location.Y);
                isMouseDown = false;
            }

            if (isMouseDown == true)
            {
                mousePos.Y = 0;
                Location = mousePos;
            }
        }

        private void frmxuanfukuang_MouseUp_1(object sender, MouseEventArgs e)
        {

            // 修改鼠标状态isMouseDown的值   
            // 确保只有鼠标左键按下并移动时，才移动窗体   
            if (e.Button == MouseButtons.Left)
            {
                //this.MouseMove -= frmxuanfukuang_MouseMove;
                isMouseDown = false;
            }
        }
        //设置窗体显示状态 
        [DllImport("user32.dll")]
        private static extern int SetWindowPos(IntPtr hwnd, int hWndInsertAfter, int x, int y, int cx, int cy, int wFlags); 
       </span>

         需要绑定上面的事件。