system.interactive

System.Interactive.dll includes a For() method with the following implementation: IEnumerable<TResult> For<TSource, TResult>( IEnumerable<TSource> source, Func<TSource, IEnumerable<TResult>> resultSelector) { return source.Select<TSource, IEnumerable<TResult>>(resultSelector).Concat<TResult>(); } Am I missing something or is this equivalent to the existing Enumerable.SelectMany() , minus this ? IEnumerable<TResult> SelectMany<TSource, TResult>( this IEnumerable<TSource> source, Func<TSource, IEnumerable<TResult>> selector) Good question. They produce the same results but the internal