ASP Repeater control with multiple templates

Question

How can I have a repeater control with multiple templates where the template chosen is based upon the type of the item?

This is what I have currently:

My repeater class:

[ToolboxData("<{0}:LifestreamRepeater runat=server>")]
public class LifestreamRepeater : Repeater
{

    [PersistenceMode(PersistenceMode.InnerProperty)]
    public ITemplate TwitterTemplate {get; set;}


    protected override void OnDataBinding(EventArgs e)
    {
        //base.OnDataBinding(e);
        foreach (var item in (IEnumerable<LifestreamItem>)this.DataSource)
        {
            if (item is LifestreamTwitterItem)
            {
                LifestreamRepeaterItem ri = new LifestreamRepeaterItem(item);
                TwitterTemplate.InstantiateIn(item);
            }
            else
            {
                ItemTemplate.InstantiateIn(item);
            }
        }

    }
}

and the front end:

        <lfs:LifestreamRepeater runat="server" ID="repeater1">
            <TwitterTemplate>
                <div class="Lifestream Twitter Item">
                    <h4> <%# DataBinder.Eval(Container.DataItem, "Title")%> </h4>
                    <p>  <%# DataBinder.Eval(Container.DataItem, "Body")%> </p>
                </div>
            </TwitterTemplate>
            <ItemTemplate>
                <div class="Lifestream Item">
                    <h2> <%# DataBinder.Eval(Container.DataItem, "Title")%> </h2>
                    <p>  <%# DataBinder.Eval(Container.DataItem, "Body")%> </p>
                </div>
            </ItemTemplate>
        </lfs:LifestreamRepeater>

Then I bind the repeater control to an IEnumerable of LifestreamItem which is a base class for multiple different social network post types so there might be TwitterLifestreamItem and VimeoLifestreamItem and I want the repeater to choose a different template, with different possible values, depending on the dataitem.

Answer 1

I don't think there's anything build into ASP.NET that allows this but you could do this:

<asp:Repeater ID="myRepeater" runat="server" OnItemDataBound="myRepeater_ItemDataBound">
    <ItemTemplate>
        <asp:PlaceHolder ID="twitterTemplate" Visible="false" runat="server">
             <asp:Literal ID="fooTwitterControl" runat="server" />
        </asp:PlaceHolder>

        <asp:PlaceHolder ID="itemTemplate" Visible="false" runat="server">
             <asp:Literal ID="fooItemControl" runat="server" />
        </asp:PlaceHolder>
    </ItemTemplate>
</asp:Repeater>

And the ItemDataBound event:

protected void myRepeater_ItemDataBound(object sender, RepeaterItemEventArgs e)
{
    if (ListItemType.Item == e.Item.ItemType || ListItemType.AlternatingItem == e.Item.ItemType)
    {
        PlaceHolder twitterTemplate = (PlaceHolder)e.Item.FindControl("twitterTemplate");
        PlaceHolder itemTemplate = (PlaceHolder)e.Item.FindControl("itemTemplate");

        var item = (LifestreamItem)e.Item.DataItem;
        if (item is LifestreamTwitterItem)
        {
            twitterTemplate.Visible = true;

            Literal fooTwitterControl = (Literal)e.Item.FindControl("fooTwitterControl");
            // Load all twitter related controls + populate
        }
        else
        {
            itemTemplate.Visible = true;
            Literal fooItemControl = (Literal)e.Item.FindControl("fooItemControl");
            // Load all non-twitter controls + populate
        }
    }
}

Essentially, the ItemTemplates become placeholders and enable/disable based on the type you're iterating over.

Answer 2

It seems that the solution is to override the DataBind method like this:

    public override void DataBind()
    {
        foreach (var item in (IEnumerable<LifestreamItem>)this.DataSource)
        {
            if (item is LifestreamTwitterItem)
            {
                TwitterTemplate.InstantiateIn(item); // instantiate inside the item which is also a control.
            }
            else
            {
                ItemTemplate.InstantiateIn(item);
            }
            item.DataBind(); // bind the item
            Controls.Add(item); // add the item to the repeater
        }
    }