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A quick guide to using nested repeaters in ASP.NET

, 19 Feb 2004 CPOL
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Using nested repeaters in ASP.NET with an XML data store

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.

License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

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About the Author

Nish Sivakumar

United States United States
Nish is a real nice guy who has been writing code since 1990 when he first got his hands on an 8088 with 640 KB RAM. Originally from sunny Trivandrum in India, he has been living in various places over the past few years and often thinks it’s time he settled down somewhere.
 
Nish has been a Microsoft Visual C++ MVP since October, 2002 - awfully nice of Microsoft, he thinks. He maintains an MVP tips and tricks web site - www.voidnish.com where you can find a consolidated list of his articles, writings and ideas on VC++, MFC, .NET and C++/CLI. Oh, and you might want to check out his blog on C++/CLI, MFC, .NET and a lot of other stuff - blog.voidnish.com.
 
Nish loves reading Science Fiction, P G Wodehouse and Agatha Christie, and also fancies himself to be a decent writer of sorts. He has authored a romantic comedy Summer Love and Some more Cricket as well as a programming book – Extending MFC applications with the .NET Framework.
 
Nish's latest book C++/CLI in Action published by Manning Publications is now available for purchase. You can read more about the book on his blog.
 
Despite his wife's attempts to get him into cooking, his best effort so far has been a badly done omelette. Some day, he hopes to be a good cook, and to cook a tasty dinner for his wife.

Comments and Discussions

 
GeneralRe: A couple of small points...this is not the most efficient method PinstaffNishant S21-Feb-04 1:22 
GeneralRe: A couple of small points...this is not the most efficient method PinsussScott Galloway21-Feb-04 1:34 
GeneralLots of text.. PinmemberRay Hayes19-Feb-04 23:32 
GeneralRe: Lots of text.. PinstaffNishant S19-Feb-04 23:45 
Ray Hayes wrote:
I'd simply solve the problem you presented with a short XSL page.
 
Hello Ray
 
I guess, by using the XML file I might have inadvertently misplaced the focus of the article from the nested repeaters to the XML data. I'll try and make things clearer using a more-real-life example.
 
Lets take CP as an example case. CP has a top level category classification – C++, ASP.NET, .NET, All topics etc. Lets assume that these categories are stored in an Excel file. Under each category we have sections where some sections might belong to multiple categories. Now assume that these sections are stored in a SQL server database (each section has a field for the top-level category. Now assume that for each section we have an XML file (or a CSV file) that lists all articles under that section.
 
Now using nested repeaters (3 levels required) we can very easily generate a page that lists all categories/sections/articles.
 
The outermost repeater binds to the excel sheet’s specific worksheet/column, the middle repeater binds to the SQL server table, and the innermost repeater binds to the XML file.
 
The outer repeater is setup to generate a combobox that lists all categories, whose onchange event is handled to generate a page using the middle repeater. The middle repeater is setup to generate tables – one table for each section. Thus depending on the category chosen in the combobox we list those sections that are associated with that top-level category. Now the inner most repeater is used to list individual articles corresponding to each section.
 
I hope I have made the example clear.
 
So its not just about XML. The repeater control is one real cool control, and nested repeaters make it even better.
 
Regards
Nish

 

Extending MFC Applications with the .NET Framework [NW]
Summer Love and Some more Cricket [NW] (My first novel)
Shog's review of SLASMC [NW]
Nish is now the first and only CPian (as of now) to reach 16,000 forum posts on CodeProject.
GeneralRe: Lots of text.. PinmemberRay Hayes19-Feb-04 23:51 
GeneralRe: Lots of text.. PinstaffNishant S21-Feb-04 1:27 
GeneralRe: Lots of text.. Pinmemberblucas200515-Mar-07 12:58 
GeneralOT: New image PinsitebuilderUwe Keim19-Feb-04 21:41 
GeneralRe: OT: New image PinstaffNishant S19-Feb-04 23:32 
GeneralRe: OT: New image PinsitebuilderUwe Keim19-Feb-04 23:34 

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