ICollection.Contains on custom types

Question

If I have a (reference - does it matter?) type MyType which does not override the Equals method, what heuristics will be used when determining if an IC

Answer 1

It's not defined by ICollection- different implementations can use different methods. From MSDN:

Implementations can vary in how they determine equality of objects; for example, List uses Comparer.Default, whereas Dictionary allows the user to specify the IComparer implementation to use for comparing keys

In most cases it will just compare the references, but you should check the documentation for the specific ICollection you are using.