I just today cracked a problem which consumed my Friday afternoon and a big chunk of this morning. This was something i hadn’t come across in .net when using repeaters before.
On the aspx side I had a repeater embedded within a repeater;
<asp:Repeater ID="rptAddedSeries" runat="server">
<headerTemplate>
<div id="seriesHeader">
</headerTemplate>
<itemTemplate>
<h2>
<%#Container.DataItem().Title%>
</h2>
<asp:Repeater ID="rptBooks" runat="server">
<headerTemplate><ul></headerTemplate>
<itemTemplate>
<li>
<%#Container.DataItem().BookID%>
</li>
</itemTemplate>
<footerTemplate>
</ul>
</footerTemplate>
</asp:Repeater>
</itemTemplate>
<footerTemplate>
</div>
</footerTemplate>
</asp:Repeater>
I simply wanted to populate the inner repeater and perform the databinding. The code i had worked fine- using FindControl to grab the inner repeater then setting the datasource and executeing DataBind(). However, when i added the HeaderTemplate and FooterTemplate to the parent “rptAddedSeries” control, the FindControl suddenly stopp working and i started getting a NullReferenceException when trying to set my DataSource.
Protected Sub rptAddedSeries_ItemDataBound(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.RepeaterItemEventArgs)Handles rptAddedSeries.ItemDataBound
Dim this_repeater_item As RepeaterItem = DirectCast(sender, Repeater).Controls.Item(_repeater_counter)
Dim child_repeater As Repeater = DirectCast(this_repeater_item.FindControl("rptBooks"), Repeater)
child_repeater.DataSource = _highlight.Highlights_Seriess(_repeater_counter).Highlight_Series_Books
child_repeater.DataBind()
_repeater_counter += 1
End Sub
After a bit of googling I found a forum post on asp.net forums by someone with a similar issue. The ItemDataBound event occurs against each part of the your repeater item- meaning if you have a HeaderTemplate and FooterTemplate as well as your standard ItemTemplate, the ItemDataBound will execute 3 times. So I added a condition at the start of the function to ensure that i was running my code only during the ItemTemplate data binding;
If e.Item.ItemType = ListItemType.Item Then ... End If
However i was still having issue’s with the FindControl failing. Reading down the same forum post i found a note mentioning that FindControl wouldn’t work directly against the RepeaterItem but there was nothing to say whatI should be running it against. Considering the it was the e (RepeaterItemEventArgs) object we tested to find the current ItemType, it stood to reason that the actual item might be contained within there so i modified the method and it worked perfectly;
Protected Sub rptAddedSeries_ItemDataBound(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.RepeaterItemEventArgs) Handles rptAddedSeries.ItemDataBound
If e.Item.ItemType = ListItemType.Item Then
'Dim this_repeater_item As RepeaterItem = DirectCast(sender, Repeater).Controls.Item(_repeater_counter)
'Dim child_repeater As Repeater = DirectCast(this_repeater_item.FindControl("rptBooks"), Repeater)
'Dim child_repeater As Repeater = DirectCast(this_repeater_item.TemplateControl.FindControl("rptBooks"), Repeater)
Dim child_repeater As Repeater = DirectCast(e.Item.FindControl("rptBooks"), Repeater)
child_repeater.DataSource = _highlight.Highlights_Seriess(_repeater_counter).Highlight_Series_Books
child_repeater.DataBind()
_repeater_counter += 1
End If
End Sub
Hope this save’s someone else a few hours of tearing their hair out!
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