How to affect differences in row content when binding a dataset to a ListView in ASP.NET 3.5

I have added a ListView to a web form and this code works when the data columns in the bound dataset have values:

<asp:ListView ID="picturesListView" runat="server"
    GroupPlaceholderID="groupsGoHere"
    ItemPlaceholderID="itemsGoHere" 
    GroupItemCount="1" >

    <LayoutTemplate>
            <p id="pictureList">Picture List:</p>
            <ol id="imagegallery">
                <asp:PlaceHolder ID="groupsGoHere" runat="server" />
            </ol>
    </LayoutTemplate>
    <GroupTemplate>
          <asp:PlaceHolder runat="server" ID="itemsGoHere" />
    </GroupTemplate>        
    <ItemTemplate>开发者_C百科;
            <li>
                <a href="<%# Eval("ImageURL")%>" title="<%#Eval("ImageDesc") %>">
                    <%#Eval("ImageDesc")%> 
                </a>
            </li>            
    </ItemTemplate>
</asp:ListView>

Then in the codebehind file, I have just these 2 lines to populate the Listview:

picturesListView.DataSource = dsImages
picturesListView.DataBind()

All rows in the dataset have a value for the ImageURL column but the ImageDesc column can be null or an empty string. How could I check to see if ImageDesc for a given row is empty and construct a "pseudo-descriptor" such as "untitled picture no. N" where N is the relative row number in the dataset. I suppose I could change the stored procedure that returns this dataset...but this seems as if it should be possible.

This could be done more gracefully, but should answer your question:

<div runat="server" visible='<%# !string.IsNullOrEmpty(Eval("ImageDesc","{0}") )%>' > 
<a href="<%# Eval("ImageURL")%>" title="<%#Eval("ImageDesc") %>">
                    <%#Eval("ImageDesc")%> 
                </a>
</div>
<div runat="server" visible='<%# string.IsNullOrEmpty(Eval("ImageDesc","{0}") )%>' >
My psuedo-descriptor
</div>