Testing a Container.DataItem with inline code

I would do this. You bind your "visibility" function to the visible property of an asp:literal control:

<asp:Repeater id="myRepeater" runat="server">
    <ItemTemplate>
        <asp:literal runat='server' id='mycontrol' 
          visible='<%# DataBinder.Eval(Container.DataItem, "MyProperty").Equals("SomeValue") %>'>
          <%# DataBinder.Eval(Container.DataItem, "MyProperty") %>
        </asp:literal>
     </ItemTemplate>
 </asp:Repeater>

You could refactor it out to server side script.

<script runat="server">
protected string ShowIfEqual(RepeaterItem Item, string SomeValue) {
   YourTypeThatIsDataBound _item = (YourTypeThatIsDataBound)Item.DataItem;
   return _item.MyProperty == SomeValue ? _item.MyProperty : string.Empty;
}
</script>

And the call it inline as...

<%#ShowIfEqual(Container, "SomeValue")%>