Repeater with Linq - One Item with many child items

Question

This is a challenging one.

I have 2 tables in the DB:

Class: Id, Class Name etc.

Student: ID, ClassID, Name etc.

I would like to have a Repeater which contains the following:

Class 1 Name

• Student 1
• Student 2

Class 2 Name

• Student 1
• Student 2

Now here's my Dilemma.

If I do a Select and Join with Linq something along these lines I get a new repeater Item for every student:

var query = (From c in Class
join s in Student on c.ID equals S.ClassID
select new {C,A}).Tolist();

However what I want is an Item for every CLASS with children items in each class as student.

Not too sure If I explained myself here... Ask questions and I'll answer.

Thank you very very much.

Answer 1

You can use a nested repeater and have the child repeater use the students of the parent class.

<asp:Repater ....>
 <asp:Repeater runat="server" DataSource='<%# Eval("Students") %>'>
 </>

It depends a bit on your datamodel, but if you have the proper FK structure you do not need to manually join to the new {}. You coud simply force eager loading on the datacontext and do a Foreach over your class

Code example found here: http://www.antiyes.com/nested-repeater

Answer 2

Something like that should work (essentially group the students before joining):

Student.GroupBy(s => s.ClassID)
       .Join(Class,
             g => g.Key,
             c => c.ID,
             (g, c) => new { Class = c, Students = g.ToArray() })
       .ToList();

The result is a list of anonymous type with Class = a given class and Students = array of Students attending that class.