c# winform 窗体移动

public const int WM_SYSCOMMAND = 0x0112;
        public const int SC_MOVE = 0xF010;
        public const int HTCAPTION = 0x0002;

        [DllImport("user32.dll", EntryPoint = "SendMessageA")]
        private static extern int SendMessage(IntPtr hwnd, int wMsg, int wParam, int lParam);

        [DllImport("user32.dll")]
        private static extern int ReleaseCapture();
 
private void Form_MouseDown(object sender, MouseEventArgs e)
        {
            ReleaseCapture();
            SendMessage(btn_rensheng.Handle, WM_SYSCOMMAND, SC_MOVE + HTCAPTION, 0);
        }