C#: How to drag a from by the form and its controls?

Question

I use the following code to drag a borderless form, by clicking and dragging the form itself. It works, but it doesn't for when you click and drag a control located on the form. I need to be able to drag it when clicked on some of the controls but not others - drag by labels, but don't by buttons and text boxes. How do I do it?

protected override void WndProc(ref Message m)
{
    base.WndProc(ref m);

    const int WM_NCHITTEST = 0x84;
    const int HTCLIENT = 0x1;
    const int HTCAPTION = 0x2;

    if (m.Msg == WM_NCHITTEST && (int)m.Result == HTCLIENT)
        m.Result = (IntPtr)HTCAPTION;
}

Answer 1

Actually, I found the solution here.

public const int WM_NCLBUTTONDOWN = 0xA1;
public const int HTCAPTION = 0x2;

[DllImport("User32.dll")]
public static extern bool ReleaseCapture();
[DllImport("User32.dll")]
public static extern int SendMessage(IntPtr hWnd, int Msg, int wParam, int lParam);

// Paste the below code in the your label control MouseDown event
if (e.Button == MouseButtons.Left)
{
    ReleaseCapture();
    SendMessage(Handle, WM_NCLBUTTONDOWN, HTCAPTION, 0);
}

it works.

Also, in my code above, if resizing is desired, if statement should be changed to

        if (m.Msg == WM_NCHITTEST)
            if ((int)m.Result == HTCLIENT)
                m.Result = (IntPtr)HTCAPTION;