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Two Approaches to Avoiding Repeating an Item Template

AspDotNetDev31-Jan-13 12:43

AspDotNetDev

31-Jan-13 12:43

An ex-cow-orker needed to create two sections on an ASP.NET webpage with repeated items. Imagine something that gets rendered to HTML like this:

HTML

<h2>First Header</h2>
  <div>Item 1</div>
  <div>Item 2</div>
<h2>Second Header</h2>
  <div>Item 3</div>
  <div>Item 4</div>
  <div>Item 5</div>

To avoid creating two repeaters, they created a single repeater, and then used the pre-render events to add headers to each section. Here's a short version of it (much simplified):

ASP.NET

<script runat="server">
  Private Sub myRepeater_PreRender(sender As Object, e As System.EventArgs) Handles myRepeater.PreRender
    For Each item In myRepeater.Items
      If SomeCondition1() Then
        Dim headerContainer As PlaceHolder = item.FindControl("myHeader")
        AddHeader(headerContainer, "First Header")
      End If
      If SomeCondition2() Then
        Dim headerContainer As PlaceHolder = item.FindControl("myHeader")
        AddHeader(headerContainer, "Second Header")
      End If
    Next
  End Sub
</script>

<asp:Repeater runat="server" ID="myRepeater">
  <ItemTemplate>
    <asp:PlaceHolder ID="myHeader" runat="server" />
    <%-- ...Rest of item template... -->
  </ItemTemplate>
</asp:Repeater>

Not a bad approach, I think, though I'd probably have just created a nested repeater:

XML

<asp:Repeater runat="server" ID="outerRepeater">
  <ItemTemplate>
    <h2><%# HttpUtility.HtmlEncode(DirectCast(Container.DataItem, ItemCollection).HeaderText) %></h2>
    <asp:Repeater runat="server" DataSource="<%# DirectCast(Container.DataItem, ItemCollection).Items %>">
      <ItemTemplate>
        <%-- ...Rest of item template... -->
      </ItemTemplate>
    </asp:Repeater>
  </ItemTemplate>
</asp:Repeater>

Of course, I'd have to split out the collection being bound to into two collections and create some wrapper classes and such, but nothing too difficult. I like this approach more, because you can avoid doing unnecessary processing during the render/binding stages (which just seems like a hack to me).

Another reason I prefer my approach is because you could then sort each collection differently. What I had to do instead was to first sort on SomeCondition1() and SomeCondition2(), then perform a secondary sort (which looks pretty awkward in LINQ).

EDIT: Fixed typo.

Thou mewling ill-breeding pignut!

modified 31-Jan-13 19:01pm.

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