C# Winform 让整个窗口都可以拖动

[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 void frmMain_MouseDown(object sender, MouseEventArgs e)
{
    ReleaseCapture();
    SendMessage(this.Handle, 0x0112, 0xF012, 0);
}

protected override void OnMouseDown(MouseEventArgs e);

protected override void OnMouseDown(MouseEventArgs e)
{
    base.OnMouseDown(e);
    frmMain_MouseDown(this, e);
}