Question

Using ASP.net 2.0, how do I present the information to the user similar to the Questions list on SO where each question has some child items (like the tags).

I would probably be making two separate queries, one to first find the list of questions, then another query to find all tags which belonged to the list of questions.

Approach 1:

Then I would probably be using nested repeaters and doing a select statement in the code-behind on each nested repeater ‘OnItemDataBind’…

Approach 2:

Or with the two datasets, I would use C# code to create a business entity of each of the ‘Questions’ and have a property called ‘Tags’. I would then loop through my tags dataset and assign the property.

What’s more efficient? Are there any other alternatives?

Answer 1

I would definitely avoid the second approach – you don’t want to hit the database everytime you databind a parent item. As DOK says, try and architect your system properly. For me that would mean populating a collection of business objects and binding to it. I do something similar with a custom menu control (note this nests three datalists, but you could use repeaters):

In the aspx page:

<asp:DataList ID='dlMenuOne' runat='server' onitemdatabound='dlMenu_ItemDataBound' >             <ItemTemplate>              //your object                  <asp:DataList ID='dlMenuTwo'  runat='server' onitemdatabound='dlMenuTwo_ItemDataBound'>                 <ItemTemplate>                 //your object's child items                      <asp:DataList ID='dlMenuThree' runat='server'>                     <ItemTemplate>                        //child item's child items                         </ItemTemplate>                     </asp:DataList>                  </ItemTemplate>                 </asp:DataList>               </ItemTemplate>             </asp:DataList> 

then in the code behind:

protected void dlMenu_ItemDataBound(object sender, DataListItemEventArgs e) {     DataListItem parentList = e.Item;     DataList dlMenuTwo = (DataList)parentList.FindControl('dlMenuTwo');     MenuItem item = (MenuItem)parentList.DataItem;     dlMenuTwo.DataSource = _menu.GetChildItems(item);     dlMenuTwo.DataBind(); } 

this method basically gets a reference to the object being bound (parentList.DataItem) and then binds the nested DataList to the child items (_menu.GetChildItems(item))