Outputcache WebUserControl not working as expected

I have a webusercontrol with the following outputcache defined:
<%@ OutputCache Duration="120" VaryByControl="SelectedMenu" Shared="true" %> Where "SelectedMenu" is a public int property of the control.
When I use the control in these three ways on the page:
<NewStore:LeftMenuLinks runat="server" SelectedCatID="<%#SelectedCatID %>" /> <NewStore:LeftMenuLinks runat="server" SelectedCatID="1" /> <NewStore:LeftMenuLinksGo to the complete details ...