Linq GroupJoin with a Func<Inner,Outer,bool> ?

Question

I have IEnumerable<A> and IEnumerable<B> I want to Group Join based on whether A.Test(B) returns true.

The keyselector funcs do not seem to do this as the KeySelectors need to return keys of the same type so that they can be checked for equality.

Is there something I'm missing here?

Answer 1

You're right, GroupJoin can't really handle this case. Will this workaround do?

var res = from aInstance in aSequence 
          select new {
                       A = aInstance,
                       MatchingBs = bSequence.Where(bInstance => aInstance.Test(bInstance))
                     };