方式1

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 void Form1_MouseDown(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, yOffset);
                isMouseDown = true;
            } 
        }

        private void Form1_MouseMove(object sender, MouseEventArgs e)
        {
            if (isMouseDown)
            {
                Point mousePos = Control.MousePosition;
                mousePos.Offset(mouseOffset.X, mouseOffset.Y);
                Location = mousePos;
            } 
        }

        private void Form1_MouseUp(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)
            {
                isMouseDown = false;
            } 
        }



方式2利用API

//窗体移动API
[DllImport("user32.dll")]
public static extern bool ReleaseCapture();
[DllImport("user32.dll")]
public static extern bool SendMessage(IntPtr hwnd, int wMsg, int wParam, int IParam);
public const int WM_SYSCOMMAND = 0x0112;
public const int SC_MOVE = 0xF010;
public const int HTCAPTION = 0x0002;
[DllImport("user32")]
private static extern int SendMessage(IntPtr hwnd, int wMsg, int wParam, IntPtr lParam);
private const int WM_SETREDRAW = 0xB;



private void Form1_MouseDown(object sender, MouseEventArgs e)
{
    if (this.WindowState == FormWindowState.Normal)
    {
        ReleaseCapture();
        SendMessage(this.Handle, WM_SYSCOMMAND, SC_MOVE + HTCAPTION, 0);
    }
}

 //窗体阴影API
        const int CS_DropSHADOW = 0x20000;
        const int GCL_STYLE = (-26);
        [DllImport("user32.dll", CharSet = CharSet.Auto)]
        public static extern int SetClassLong(IntPtr hwnd, int nIndex, int dwNewLong);
        [DllImport("user32.dll", CharSet = CharSet.Auto)]
        public static extern int GetClassLong(IntPtr hwnd, int nIndex);


        public Form1()
        {
            InitializeComponent();
            SetClassLong(this.Handle, GCL_STYLE, GetClassLong(this.Handle, GCL_STYLE) | CS_DropSHADOW);
        }

winfrom的两种拖拽方式和界面阴影