Use LINQ to concatenate multiple rows into single row (CSV property)

Question

I'm looking for the LINQ equivalent to the Sybase's LIST() or MySQL's group_concat()

It'll convert:

User  Hobby
--------------
Bob   Football 
Bob   Golf 
Bob   Tennis 
Sue   Sleeping 
Sue   Drinking

To:

User  Hobby
--------------
Bob   Football, Golf, Tennis 
Sue   Sleeping, Drinking

Answer 1

That's the GroupBy operator. Are you using LINQ to Objects?

Here's an example:

using System;
using System.Collections.Generic;
using System.Linq;

public class Test
{
    static void Main()
    {
        var users = new[]
        {
            new { User="Bob", Hobby="Football" },
            new { User="Bob", Hobby="Golf" },
            new { User="Bob", Hobby="Tennis" },
            new { User="Sue", Hobby="Sleeping" },
            new { User="Sue", Hobby="Drinking" },
        };

        var groupedUsers = users.GroupBy(user => user.User);

        foreach (var group in groupedUsers)
        {
            Console.WriteLine("{0}: ", group.Key);
            foreach (var entry in group)
            {
                Console.WriteLine("  {0}", entry.Hobby);
            }
        }
    }
}

That does the grouping - can you manage the rest yourself?