Question

I use interfaces for decoupling my code. I am curious, is the usage of explicit interface implementation meant for hiding functionality?

Example:

public class MyClass : IInterface
{
     void IInterface.NoneWillCall(int ragh) { }
}

What is the benefit and specific use case of making this available only explicitly via the interface?

Answer 1

There are two main uses for it in my experience:

• It allows you to overload methods by return value. For example, IEnumerable<T> and IEnumerable both declare GetEnumerator() methods, but with different return types – so to implement both, you have to implement at least one of them explicitly. Of course in this question both methods are provided by interfaces, but sometimes you just want to give a “normal” method with a different type (usually a more specific one) to the one from the interface method.
• It allows you to implement part of an interface in a “discouraging” way – for example, ReadOnlyCollection<T> implements IList<T>, but “discourages” the mutating calls using explicit interface implementation. This will discourage callers who know about an object by its concrete type from calling inappropriate methods. This smells somewhat of interfaces being too broad, or inappropriately implemented – why would you implement an interface if you couldn’t fulfil all its contracts? – but in a pragmatic sense, it can be useful.