/// <summary>The legacy distinct by.</summary>
/// <param name="source">The source.</param>
/// <param name="keySelector">The key selector.</param>
/// <typeparam name="TSource">Source type</typeparam>
/// <typeparam name="TKey">Key type</typeparam>
/// <returns>the unique list</returns>
public static IEnumerable <TSource> LegacyDistinctBy <TSource, TKey>(this IEnumerable <TSource> source, Func <TSource, TKey> keySelector)
where TKey : IEquatable <TKey>
{
return(source.Distinct(DelegateEqualityComparer <TSource> .CompareMember(keySelector)));
}
