LINQ DistinctBy

LINQDistinctBy.cs

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

public static class LINQExtension
{
	public static IEnumerable<TSource> DistinctBy<TSource, TKey>
		(this IEnumerable<TSource> source, Func<TSource, TKey> keySelector)
	{
		HashSet<TKey> knownKeys = new HashSet<TKey>();
		foreach (TSource element in source)
		{
			if (knownKeys.Add(keySelector(element)))
			{
				yield return element;
			}
		}
	}
}