How can I hide a repeater in ASP.NET C# if the DataSource contains no items?

Question

I have an ASP.NET page that uses a repeater nested within another repeater to generate a listing of data. It's to the effect of the following:

<asp:Repeater>
    <ItemTemplate>
        <span><%#Eval("Data1") %></span>
        <!-- and many more -->
        <asp:Repeater DataSource='<%#Eval("Data2")%>'>
            <HeaderTemplate>
                <ul>
            </HeaderTemplate>
            <ItemTemplate>
                <li><%#Container.DataItem%></li>
            </ItemTemplate>
            <FooterTemplate>
                </ul>
            </FooterTemplate>
        </asp:Repeater>
    </ItemTemplate>
</asp:Repeater>

In the (C#) code-behind I'm basically using LINQ to pull a listing of information from an XML document and bind that information to the first repeater.

Searching for the answer to this, it seems the method is to determine whether the data for the nested repeater is empty. If it is, then you set the visibility of the repeater to false.

Unfortunately, I haven't been able to determine how to do that inline, and not in the code-behind (since it won't necessarily work for what I'm doing).

Since my pages aren't validating now, because the ul ends up being empty for any items without Data2, and because I'd like to keep using an unordered list, I seek your help.

Any ideas?

Thanks!

UPDATE:

If it helps, since it could very well be possible to do in the code-behind, the LINQ is something to this effect:

var x = from y in z
    select new {
        Data1 = d,
        // etcetera
        Data2 = (from j in k
            where j.Value != String.Empty
            select j.Value).ToList()
    };

blah.DataSource = x;
blah.DataBind();

Answer 1

This won't hide the repeater completely, but you can subclass the Repeater control so that it includes a GridView-like empty data template:

using System;
using System.Web.UI;
using System.Web.UI.WebControls;

public class EmptyCapableRepeater : Repeater
{
    public ITemplate EmptyDataTemplate { get; set; }

    protected override void OnDataBinding ( EventArgs e )
    {
        base.OnDataBinding( e );

        if ( this.Items.Count == 0 )
        {
            EmptyDataTemplate.InstantiateIn( this );
        }
    }
}

You can them use it in your .aspx like this:

<custom:EmptyCapableRepeater runat="server" ID="rptSearchResults">
    <ItemTemplate>
        <%# Eval( "Result" )%>
    </ItemTemplate>
    <SeparatorTemplate>
        <br />
    </SeparatorTemplate>
    <EmptyDataTemplate>
        <em>No results were found.</em>
    </EmptyDataTemplate>
</custom:EmptyCapableRepeater>