LINQ's Distinct() on a particular property

Question

I am playing with LINQ to learn about it, but I can\'t figure out how to use Distinct when I do not have a simple list (a simple list of integers is pretty easy

Answer 1

The following code is functionally equivalent to Jon Skeet's answer.

Tested on .NET 4.5, should work on any earlier version of LINQ.

public static IEnumerable DistinctBy(
  this IEnumerable source, Func keySelector)
{
  HashSet seenKeys = new HashSet();
  return source.Where(element => seenKeys.Add(keySelector(element)));
}

Incidentially, check out Jon Skeet's latest version of DistinctBy.cs on Google Code.