public static MonadOr <TResult> Join <TSource, TInner, TKey, TResult>(
this MonadOr <TSource> @this,
MonadOr <TInner> inner,
Func <TSource, TKey> outerKeySelector,
Func <TInner, TKey> innerKeySelector,
Func <TSource, TInner, TResult> resultSelector,
IEqualityComparer <TKey> comparer)
{
Require.NotNull(@this, nameof(@this));
Require.NotNull(inner, nameof(inner));
Require.NotNull(resultSelector, nameof(resultSelector));
Require.NotNull(outerKeySelector, nameof(outerKeySelector));
Require.NotNull(innerKeySelector, nameof(innerKeySelector));
var lookup = GetKeyLookup(inner, innerKeySelector, comparer);
Func <TSource, MonadOr <TInner> > valueSelector = outer => lookup(outerKeySelector(outer));
return(@this.SelectMany(valueSelector, resultSelector));
}
