In ASP.NET, using VB, how can i do this on the page itself, not in the code behind?
<ItemTemplate>
<% If Container.DataItem("filename") <> "" Then
<a href="/pdf/"><%# Container.DataItem("filename") %>Agenda</a>
End If%>
</ItemTemplate>
Create a boolean property in your data source e.g. filenameExists and use this to databind against the Visible property of a HyperLink