Resize borderless window on bottom right corner

I'd like the user to resize a borderless window on bottom right corner like I can resize the autocomplete window of the combobox control.

I cannot find the properties to configure a form that way.

Maybe someone could help me on the problem.

An image could be found here:

Here's the code corresponding to Franci's explanations, I was writing it but he answered meanwhile so vote up his explanation which is good if this code suits your needs.

protected override void WndProc(ref Message m) {
    const int wmNcHitTest = 0x84;
    const int htBottomLeft = 16;
    const int htBottomRight = 17;
    if (m.Msg == wmNcHitTest) {
        int x = (int) (m.LParam.ToInt64() & 0xFFFF);
        int y = (int) ((m.LParam.ToInt64() & 0xFFFF0000) >> 16);
        Point pt = PointToClient(new Point(x, y));
        Size clientSize = ClientSize;
        if (pt.X >= clientSize.Width - 16 && pt.Y >= clientSize.Height - 16 && clientSize.Height >= 16) {
            m.Result = (IntPtr) (IsMirrored ? htBottomLeft : htBottomRight);
            return;
        }
    }
    base.WndProc(ref m);
}

Edit: to write the gripper, you can initialize a new VisualStyleRenderer(VisualStyleElement.Status.Gripper.Normal) and use its PaintBackground() method.

Thanks so much for posting this great sample and explanation. I've added some additions below that others might be interested in. Some of the code here came from other stackoverflow postings, but to be able to see it in one code block might be helpful to others. I wanted to be able to resize the form on ALL borders, not just the lower right corner. I also wanted to be able to drag the form around. Lastly, I wanted a drop-shadow.

//***********************************************************
//This gives us the ability to resize the borderless from any borders instead of just the lower right corner
protected override void WndProc(ref Message m)
{
    const int wmNcHitTest = 0x84;
    const int htLeft = 10;
    const int htRight = 11;
    const int htTop = 12;
    const int htTopLeft = 13;
    const int htTopRight = 14;
    const int htBottom = 15;            
    const int htBottomLeft = 16;
    const int htBottomRight = 17;          

    if (m.Msg == wmNcHitTest)
    {
        int x = (int)(m.LParam.ToInt64() & 0xFFFF);
        int y = (int)((m.LParam.ToInt64() & 0xFFFF0000) >> 16);
        Point pt = PointToClient(new Point(x, y));
        Size clientSize = ClientSize;
        ///allow resize on the lower right corner
        if (pt.X >= clientSize.Width - 16 && pt.Y >= clientSize.Height - 16 && clientSize.Height >= 16)
        {           
            m.Result = (IntPtr)(IsMirrored ? htBottomLeft : htBottomRight);
            return;
        }       
        ///allow resize on the lower left corner
        if (pt.X <= 16 && pt.Y >= clientSize.Height - 16 && clientSize.Height >= 16)
        {
            m.Result = (IntPtr)(IsMirrored ? htBottomRight : htBottomLeft);
            return;
        }
        ///allow resize on the upper right corner
        if (pt.X <= 16 && pt.Y <= 16 && clientSize.Height >= 16)
        {
            m.Result = (IntPtr)(IsMirrored ? htTopRight : htTopLeft);
            return;
        }
        ///allow resize on the upper left corner
        if (pt.X >= clientSize.Width - 16 && pt.Y <= 16 && clientSize.Height >= 16)
        {
            m.Result = (IntPtr)(IsMirrored ? htTopLeft : htTopRight);
            return;
        }
        ///allow resize on the top border
        if (pt.Y <= 16 && clientSize.Height >= 16)
        {
            m.Result = (IntPtr)(htTop);
            return;
        }
        ///allow resize on the bottom border
        if (pt.Y >= clientSize.Height - 16 && clientSize.Height >= 16)
        {
            m.Result = (IntPtr)(htBottom);
            return;
        }
        ///allow resize on the left border
        if (pt.X <= 16 && clientSize.Height >= 16)
        {
            m.Result = (IntPtr)(htLeft);
            return;
        }
        ///allow resize on the right border
        if (pt.X >= clientSize.Width - 16 && clientSize.Height >= 16)
        {
            m.Result = (IntPtr)(htRight);
            return;
        }
    }
    base.WndProc(ref m);
}
//***********************************************************
//***********************************************************
//This gives us the ability to drag the borderless form to a new location
public const int WM_NCLBUTTONDOWN = 0xA1;
public const int HT_CAPTION = 0x2;

[DllImportAttribute("user32.dll")]
public static extern int SendMessage(IntPtr hWnd, int Msg, int wParam, int lParam);
[DllImportAttribute("user32.dll")]
public static extern bool ReleaseCapture();

private void YOURCONTROL_MouseDown(object sender, MouseEventArgs e)
{
    //ctrl-leftclick anywhere on the control to drag the form to a new location 
    if (e.Button == MouseButtons.Left && Control.ModifierKeys == Keys.Control)
    {       
        ReleaseCapture();
        SendMessage(Handle, WM_NCLBUTTONDOWN, HT_CAPTION, 0);
    }  
}
//***********************************************************
//***********************************************************
//This gives us the drop shadow behind the borderless form
private const int CS_DROPSHADOW = 0x20000;
protected override CreateParams CreateParams
{
    get
    {
        CreateParams cp = base.CreateParams;
        cp.ClassStyle |= CS_DROPSHADOW;
        return cp;
    }
}
//***********************************************************