OpenTK Change Viewport Size While Resizing

Question

I'm making a GUI framework with OpenTK and SharpFont, so I need the viewport size to change while the user is resizing the window and not just after the user lets go of the mouse button. How can I do this? Do I need to override the Run() method for NativeWindow?

// only called after user lets go of the mouse cursor, not while resizing
protected override void OnResize(ResizeEventArgs e)
{
    base.OnResize(e);

    GL.Viewport(0, 0, e.Width, e.Height);
}