How do I group in memory lists?

Question

I have a list of Foo. Foo has properties Bar and Lum. Some Foos have identical values for Bar. How can I use lambda/linq to group my Foos by Bar so I can iterate over each grouping's Lums?

Answer 1

var q = from x in list
        group x by x.Bar into g
        select g;

foreach (var group in q)
{
    Console.WriteLine("Group " + group.Key);
    foreach (var item in group)
    {
        Console.WriteLine(item.Bar);
    }
}