You can access the value of this id using InnerText property. then apply condition on it set visible property to true i.e
on page
<ul runat="server" id="a">
<li id="b" runat="server" visible="false">Test</li>
</ul>
on code side
if (b.InnerText == "Test")
{
b.Visible = true;
b.InnerText = "Text";
}
hope u got the idea.