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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 Nishant

United States United States
Nish Nishant is a Software Architect/Consultant based out of Columbus, Ohio. He has over 15 years of software industry experience in various roles including Lead Software Architect, Principal Software Engineer, and Product Manager. Nish is a recipient of the annual Microsoft Visual C++ MVP Award since 2002 (13 consecutive awards as of 2014).

Nish is an industry acknowledged expert in the Microsoft technology stack. He authored
C++/CLI in Action for Manning Publications in 2005, and had previously co-authored
Extending MFC Applications with the .NET Framework for Addison Wesley in 2003. In addition, he has over 140 published technology articles on CodeProject.com and another 250+ blog articles on his
WordPress blog. Nish is vastly experienced in team management, mentoring teams, and directing all stages of software development.

Contact Nish : You can reach Nish on his google email id voidnish.

Website and Blog

Comments and Discussions

 
GeneralAn alternative PinmemberIan Darling21-Feb-04 2:30 
GeneralRe: An alternative PinsussScott Galloway21-Feb-04 2:39 
GeneralRe: An alternative PinmemberIan Darling21-Feb-04 2:42 
GeneralA couple of small points...this is not the most efficient method PinmemberScott Galloway21-Feb-04 1:46 
GeneralRe: A couple of small points...this is not the most efficient method PinstaffNishant S21-Feb-04 2:22 
GeneralRe: A couple of small points...this is not the most efficient method PinsussScott Galloway21-Feb-04 2:34 
GeneralLots of text.. PinmemberRay Hayes20-Feb-04 0:32 
GeneralRe: Lots of text.. PinstaffNishant S20-Feb-04 0:45 
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 Hayes20-Feb-04 0:51 
GeneralRe: Lots of text.. PinstaffNishant S21-Feb-04 2:27 
GeneralRe: Lots of text.. Pinmemberblucas200515-Mar-07 13:58 
GeneralOT: New image PinsitebuilderUwe Keim19-Feb-04 22:41 
GeneralRe: OT: New image PinstaffNishant S20-Feb-04 0:32 
GeneralRe: OT: New image PinsitebuilderUwe Keim20-Feb-04 0:34 
GeneralRe: OT: New image PinmemberJonny Newman20-Feb-04 3:38 
GeneralRe: OT: New image PinmemberShog921-Feb-04 16:31 
GeneralRe: OT: New image PinmemberJonny Newman22-Feb-04 2:33 

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