bool need_span = ControlStyleCreated && !ControlStyle.IsEmpty;
bool enabled = IsEnabled;
if (!enabled) {
-#if NET_4_0
if (!RenderingCompatibilityLessThan40)
ControlStyle.PrependCssClass (DisabledCssClass);
else
-#endif
w.AddAttribute (HtmlTextWriterAttribute.Disabled, "disabled", false);
need_span = true;
}