Nested grid woes

I've done nested grids before, something like this:

<asp:Repeater ID="CatRepeater" Runat="Server">
 <ItemTemplate>
  <p><%# Eval("Name") %></p>
  <asp:GridView ID="ForumGrid" Runat="Server" AutoGenerateColumns="true" AllowPaging="false"
  DataSource='<%# new Category(Convert.ToInt32(Eval("CategoryID"))).GetForumCollection(false, false) %>'>
  </asp:GridView>
 </ItemTemplate>
</asp:Repeater>

I tried to do it in a more event driven manner today like this:

<script runat="server">
 void Page_Load(object sender, EventArgs e)
 {
  CategoryCollection c = Category.GetCategories(false);
  c.Insert(0, new Category(0));
  CatRepeater.DataSource = c;
  CatRepeater.DataBind();
 }

 void CatRepeater_ItemDataBound(object sender, RepeaterItemEventArgs e)
 {
  GridView g = (GridView)e.Item.FindControl("ForumGrid");
  ForumCollection f = ((Category)e.Item.DataItem).GetForumCollection(false, false);
  g.DataSource = f;
  g.DataBind();
  Trace.Warn(g.Rows.Count.ToString());
  Trace.Warn(f.Count.ToString());
 }
</script>
...
<asp:Repeater ID="CatRepeater" Runat="Server" OnItemDataBound="CatRepeater_ItemDataBound">
 <ItemTemplate>
  <p><%# Eval("Name") %></p>
  <asp:GridView ID="ForumGrid" Runat="Server" AutoGenerateColumns="true" AllowPaging="false">
  </asp:GridView>
 </ItemTemplate>
</asp:Repeater>

Here's what I don't get. In the two traces of the binding handler, the rows in the grid return 0 after databinding, yet the ForumCollection does indeed show the actual count. Am I missing something?

This is actually going to change later on, because I don't want to be making multiple hits to the data every time, but I'm experimenting with something else.