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Winforms - Click/drag anywhere in the form to move it as if clicked in the form caption [duplicate]

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.net

winforms

I am creating a small modal form that is used in Winforms application. It is basically a progress bar of sorts. But I would like the user to be able to click anywhere in the form and drag it to move it around on the desktop while it is still being displayed.

How can I implement this behavior?

like image 945
Joseph Daigle Avatar asked Aug 27 '08 13:08

Joseph Daigle


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2 Answers

Microsoft KB Article 320687 has a detailed answer to this question.

Basically, you override the WndProc method to return HTCAPTION to the WM_NCHITTEST message when the point being tested is in the client area of the form -- which is, in effect, telling Windows to treat the click exactly the same as if it had occured on the caption of the form.

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

protected override void WndProc(ref Message m)
{
    switch(m.Msg)
    {
        case WM_NCHITTEST:
        base.WndProc(ref m);

        if ((int)m.Result == HTCLIENT)
            m.Result = (IntPtr)HTCAPTION;
        return;
    }

    base.WndProc(ref m);
}
like image 174
Timothy Fries Avatar answered Sep 30 '22 20:09

Timothy Fries


Here is a way to do it using a P/Invoke.

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);

void Form_Load(object sender, EventArgs e)
{
   this.MouseDown += new MouseEventHandler(Form_MouseDown);  
}

void Form_MouseDown(object sender, MouseEventArgs e)
{                        
    if (e.Button == MouseButtons.Left)
    {
        ReleaseCapture();
        SendMessage(Handle, WM_NCLBUTTONDOWN, HTCAPTION, 0);
    }
}
like image 37
FlySwat Avatar answered Sep 30 '22 19:09

FlySwat