无边框窗体，鼠标移动窗体

[DllImport("user32.dll")]
public static extern bool ReleaseCapture();

[DllImport("user32.dll")]
public static extern bool SendMessage(IntPtr hwnd, int wMsg, int wParam, int lParam);

private const int VM_NCLBUTTONDOWN = 0XA1;//定义鼠标左键按下
private const int HTCAPTION = 2;


/// <summary>
/// 鼠标按下
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
private void panel1_MouseDown(object sender, MouseEventArgs e)
{
    //为当前应用程序释放鼠标捕获
    ReleaseCapture();
    //发送消息 让系统误以为在标题栏上按下鼠标
    SendMessage((IntPtr)this.Handle, VM_NCLBUTTONDOWN, HTCAPTION, 0);
}