If you use for example a Repeater and you do not want to show some field from the DataSource based on a expression, you could use the following solution. This example hides the year when the year in the DataSource is zero.

<asp:Repeater runat="server" id="rptGroup">
   <HeaderTemplate>
      <table>
   </HeaderTemplate>
   <ItemTemplate>
      <tr><td>
         <asp:Label id="lbl" runat="server" 
            Visible='<%#DisplayYear(DataBinder.Eval(Container.DataItem, "year"))%>'>
            <%#DataBinder.Eval(Container.DataItem, "year")%>
         </asp:Label>
      </td></tr>
   </ItemTemplate>
   <FooterTemplate>
      </table>
   </FooterTemplate>
</asp:Repeater>

In the code-behind the following method is added:

public bool DisplayYear(object item)
{
   int year = 0;

   try
   {
      year = Convert.ToInt32(item);
   }
   catch(exception)
   {
   }

   return year != 0;
}