How to search the same object with different Equal concepts?

Question

I have several objects that depending on the use case are considered Equal differently.

I need to use these objects as keys for dictionaries and as far as I know Dictionary<> use the Equals() method which limits me to have only one implementation of it.

Is there any workaround to this? I expected to be able to inject a EqualityComparer, a delegate or something so Dictionary<> can use different ways of searching for items.

Thanks.

Answer 1

Any one dictionary can only have a single equality comparer. You can't ask it to find a key with respect to a particular equality comparer, because otherwise its stored hash codes will be useless, and it would have to just do a linear search.

If you have multiple equality comparers you want to search across, I'd keep several separate dictionaries, each with a different comparer.

(If you just wanted to be able to specify the equality comparer and had missed it, that's what the Dictionary(IEqualityComparer<TKey> comparer) constructor is for).