현재 포커스 컨트롤러 찾기

public static Control FindFocusedControl(Control container)
{
    foreach (Control childControl in container.Controls) {
        if (childControl.Focused) {
            return childControl;
        }
    }

    foreach (Control childControl in container.Controls) {
        Control maybeFocusedControl = FindFocusedControl(childControl);
        if (maybeFocusedControl != null) {
            return maybeFocusedControl;
        }
    }

    return null; // Couldn't find any, darn!
}