Question

I have read

When should I choose inheritance over an interface when designing C# class libraries?

I believe I understand is-a vs must-do relationship. Having said all that here is my dilemma.

I want to implement a Collection of key value pairs most likely object. I need to add to the add and remove events only to do validation, check for duplication and some tracking stuff.

If I implement IDictionary it seems that it is a bit of an over kill to implement all the Idictionary<>, ICollection<>, IEnumerable<>, and IEnumerable. Yes most of them are one liners.

It is not recommended to inherit from Dictionary as it was never meant to be extended, shadowing the Add and remove.

Finally I can just implement a private variable and then expose the methods I want or need for the project

Any suggestions on the direction to go?

Answer 1

You should use composition and encapsulate a dictionary inside your class (the private variable option). This way, you only expose to the outside world the operations that make sense for your object and the fact that you use a dictionary is a mere implementation detail.

You should only implement IDictionary<,> or inherit from Dictionary<,> if your class is a generic dictionary with some special characterists.