public static IEnumerable <TResult> GroupJoin <TOuter, TInner, TKey, TResult, TCompareKey>(this IEnumerable <TOuter> outer, IEnumerable <TInner> inner, Func <TOuter, TKey> outerKeySelector, Func <TInner, TKey> innerKeySelector, Func <TOuter, IEnumerable <TInner>, TResult> resultSelector, Func <TKey, TCompareKey> compareKeySelector)
{
return(outer.GroupJoin(inner, outerKeySelector, innerKeySelector, resultSelector, AnonymousComparer.Create(compareKeySelector)));
}