Setting a asp repeater data source - asp.net

Question

I have a asp.net repeater control in a aspx page, with runat="server" and an id set, however for some reason i can't access its ID from code behind (I can access the id of the asp:detaislview control it sits in though). So instead in the page_load method I am doing the following:
Repeater repeater = (Repeater)PromotionSitesDetailsView.FindControl("estateRepeater");
repeater.DataSource = estateList;
However when run, an error comes up saying the repeater is null! All I want to do is set the datasource of this repeater to a List object. Any ideas?

Answer 1

You said the Repeater sits inside a DataList. The DataList is, itself, a kind of repeater - the controls inside of it don't exist until the DataList is bound to a datasource, and the controls in the template are created once per item in the source. So if you bind the DataList to a source with 3 items, you will get 3 repeaters.
So it looks kind of like this:
Page
MyDataList
Item0
MyRepeater
Item1
MyRepeater
Item2
MyRepeater
So obviously MyDataList.FindControl("MyRepeater") can't work - which "MyRepeater" are we talking about? Since multiple controls cannot have the same ID, ASP.NET solves this by making the ID unique to something called a NamingContainer. Since the DataList repeats the same set of controls many times (once per item in the data source), each item in the DataList is a NamingContainer.
We need to find the NamingContainer we know holds the instance of MyRepeater that we want:
MyDataList.Items[0].FindControl("MyRepeater");
You can iterate over the items in the DataList after it has been bound (of course, before it has been bound it has no items). You can also operate on a given item in the DataList as that item is being created:
<asp:DataList OnItemDataBound="MyDataList_HandleItemDataBound" ... />
//this will get called once per item as it is created
void MyDataList_HandleItemDataBound(object sender, DataListItemEventArgs e)
{
//e.Item is the current item being databound
Repeater myRepeater = e.Item.FindControl("MyRepeater") as Repeater;
myRepeater.DataSource = //ds
myRepeater.DataBind();
}

Answer 2

You can do it without code-behind, simply by assigning the Repeater DataSource. Here is an example of a two level hierarchical menu:
<ul>
<asp:Repeater ID="ctlMenu" runat="server">
<ItemTemplate>
<li>
<asp:HyperLink runat="server"
NavigateUrl='<%#(Container.DataItem as MyPage).GetUrl()%>'
Text="<%# (Container.DataItem as MyPage).GetName() %>"></asp:HyperLink>
<ul>
<asp:Repeater runat="server" DataSource="<%# (Container.DataItem as MyPage).GetChildren() %>">
<ItemTemplate>
<li>
<asp:HyperLink runat="server"
NavigateUrl='<%#(Container.DataItem as MyPage).GetUrl()%>'
Text="<%# (Container.DataItem as MyPage).GetName() %>"></asp:HyperLink>
</li>
</ItemTemplate>
</asp:Repeater>
</ul>
</ItemTemplate>
</asp:Repeater>
</ul>