C#

protected void WndNCCalcSize(ref Message m)
{
    NativeMethods.NCCALCSIZE_PARAMS para = new NativeMethods.NCCALCSIZE_PARAMS();
    NativeMethods.RECT winRect;

    if (m.WParam == IntPtr.Zero)
        winRect = (NativeMethods.RECT)Marshal.PtrToStructure(m.LParam, typeof(NativeMethods.RECT));
    else
    {
        para = (NativeMethods.NCCALCSIZE_PARAMS)Marshal.PtrToStructure(m.LParam, typeof(NativeMethods.NCCALCSIZE_PARAMS));
        winRect = para.rgrc0;
    }

    IntPtr HDC = NativeMethods.GetWindowDC(this.Handle);

    // Here's where I believe i'm having issues. It'll always continuosly reduce here because it's resizing the window
    // I know if I set the winRect.Top and winRect.Bottom to resize parallel to each other it'll work okay
    // But then it won't display the border. Any ideas? :\
    winRect.Top = winRect.Top + CaptionHeight;
    winRect.Bottom = winRect.Bottom - 3;
    winRect.Left = winRect.Left + 2;
    winRect.Right = winRect.Right - 2;

    this.BRect = winRect;

    if (m.WParam == IntPtr.Zero)
        Marshal.StructureToPtr(winRect, m.LParam, false);
    else
    {
        para.rgrc0 = winRect;
        Marshal.StructureToPtr(para, m.LParam, false);
    }

    NativeMethods.ReleaseDC(this.Handle, HDC);

    m.Result = new IntPtr(NativeMethods.WVR_REDRAW);

    base.WndProc(ref m);
}