Something I struggled with early in my ASP.net development was how to handle ItemDataBound event (or any repeater event) when it was inside another repeater in the code behind logic. I am presenting my code here so that it may be of use to anyone else having the same problem.

Given MyPage.aspx

   
My Repeater

   
   
     
       
       
        
       
     
   

Given MyPage.aspx.vb

' **** Please note functions CategoriesDataLayer.GetList() And ItemsDataLayer.GetCategories(CategoryId)
' ****   are used for demonstration only.  You may use any collection of data (datatable, collection, etc)    

Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
      rptMyOuterRepeater.DataSource = CategoriesDataLayer.GetList()
      rptMyOuterRepeater.DataBind()
End Sub

Protected Sub rptMyOuterRepeater_ItemDataBound(ByVal sender As Object, ByVal e As RepeaterItemEventArgs) Handles rptMyOuterRepeater.ItemDataBound
      ' Exit function if this is not in ItemTemplate
      If Not e.Item.ItemType = ListItemType.AlternatingItem AndAlso Not e.Item.ItemType = ListItemType.Item Then Exit Sub
      Dim rptMyInnerRepeater As Repeater = e.Item.FindControl("rptMyInnerRepeater")
      rptMyInnerRepeater.DataSource = ItemsDataLayer.GetItemsByCategory(e.Item.DataItem("CategoryId"))
      AddHandler rptMyInnerRepeater.ItemDataBound, AddressOf rptMyInnerRepeater_ItemDataBound
      rptMyInnerRepeater.DataBind()
End Sub

Protected Sub rptMyInnerRepeater_ItemDataBound(ByVal sender As Object, ByVal e As RepeaterItemEventArgs)
      ' Exit function if this is not in ItemTemplate
      If Not e.Item.ItemType = ListItemType.AlternatingItem AndAlso Not e.Item.ItemType = ListItemType.Item Then Exit Sub
      CType(e.Item.FindControl("ltlItem"), Literal).Text = e.Item.DataItem("ItemName")
End Sub