string format question

[Amir]

hey every one i had a question
i have a page where i display employees profiles

this page calle profile.aspx is only accessable by admins and has an ifram
where points to deatils.aspx

now i display employees names by using links in profile.aspx and i want to
display the deatils in details.aspx page which is within profile.aspx in an
ifram now i have a problem

can someone tell me why isnot this working

a herf=' <%#
String.Format("details.aspx?id={0}",Container.DataItem("u_id"))%>'>
<%# Container.DataItem("LastName")%>
/a>

i get the error saying

Compiler Error Message: CS0118:
'System.Web.UI.WebControls.RepeaterItem.DataItem' denotes a 'property' where
a 'method' was expected