[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;

//添加事件

protected void Form_MouseDown(object sender, MouseEventArgs e)
{
ReleaseCapture();
SendMessage(this.Handle, WM_SYSCOMMAND, SC_MOVE + HTCAPTION, 0);
}