A quick guide to using nested repeaters in ASP.NET

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Introduction

I've never really been much of a web-developer and never thought I'd find web-development all that interesting. But I must say I've been quite fascinated by what little ASP.NET I've done up till now, which is not a lot to be honest. One control I found particularly useful was the Repeater control, but I struggled a little when I tried to implement nested repeaters using an XML file as the data store. Eventually, the solution turned out to be embarrassingly easy, and I thought I'd write a little article for other first-timers who might encounter the same annoying situation I did.

Note to readers

I assume that you already know how to use a Repeater control. This article only shows you how to implement nested repeaters and will not attempt to explain repeaters in general.

Example

I am going to demonstrate a simple ASP.NET web application that will list out a Cricket World XI using an XML file as the input-data. Eventually, modification of the team simply involves a change in the XML file with no changes required either in the aspx pages or in the code-behind files.

My XML file

Essentially I have four categories - and each category has one or more players.

Implementing nested repeaters

I am going to list the categories first and inside each category I will list the players under that category. Lets first add the outter repeater that will list the categories.

We now add the inner repeater to the <ItemTemplate> tag of the outter repeater.

Writing the code-behind code

Alright, I know that "code-behind code" sounds weird, but I couldn't think of anything better sounding and if anyone has any better ideas, please drop me a line. Anyway we setup the first repeater in the Page_Load event handler as usual.

private void Page_Load(object sender, System.EventArgs e)
{
    DataSet ds = new DataSet();
    ds.ReadXml(MapPath("./XMLFile1.xml"));
    CategoryRepeater.DataSource = ds;
    CategoryRepeater.DataBind();
}

For setting up the outter repeater, we handle the ItemDataBound event of the Repeater class which is raised when an item is data-bound but before it is rendered on the page. We now get a reference to the PlayerRepeater control using RepeaterItem.FindControl and set its data source using CreateChildView and the automatic relation that's made for us - category_cricketer. By the way I was quite impressed by that, I never expected automatic relations to be created based on the XML. Pretty cool I think!

private void CategoryRepeater_ItemDataBound(object sender, 
    System.Web.UI.WebControls.RepeaterItemEventArgs e)
{
    RepeaterItem item = e.Item;
    if( (item.ItemType == ListItemType.Item) ||
        (item.ItemType == ListItemType.AlternatingItem) )
    {
        PlayerRepeater = (Repeater) item.FindControl("PlayerRepeater");
        DataRowView drv = (DataRowView)item.DataItem;
        PlayerRepeater.DataSource = drv.CreateChildView("category_cricketer");
        PlayerRepeater.DataBind();
    }
}

That's all.

The output

I got the below output when I viewed the web-form in my browser.

Conclusion

Feedback and criticism is welcome as usual. I'd also like to thank Aravind Corera (Chennai based C# MVP) who gave me the right URLs to solve this problem when I was tearing my hair out in frustration.

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