You can’t do something like this:

<asp:Label id="lbl1" runat="server" Text=<%= CurrentUserName %> />

That is because it won’t let you assign a server tag result to the attribute of a server control.

Thankfully, there is a solution:

http://weblogs.asp.net/infinitiesloop/archive/2006/08/09/The-CodeExpressionBuilder.aspx