Fastest way to Remove Duplicate Value from a list<> by lambda

Question

what is fastest way to remove duplicate values from a list. Assume List longs = new List { 1, 2, 3, 4, 3, 2, 5 }; So I am interesting in

Answer 1

You can use this extension method for enumerables containing more complex types:

IEnumerable distinctList = sourceList.DistinctBy(x => x.FooName);

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