Overriding interface method return type with derived class in implementation

Question

I am trying to implement (C#) an interface method in a class, returning a derived type instead of the base type as defined in the interface:

interface IFacto         


        

Answer 1

There are 2 ways to accomplish this. You can either use generics or explicitly implement interface members.

Generics

interface IFactory where T: BaseCar
{
    T GetCar();
}

class MyFactory : IFactory
{
    MyCar GetCar()
    {
    }
}

Explicitly implemented members

interface IFactory
{
    BaseCar GetCar();
}

class MyFactory : IFactory
{
    BaseCar IFactory.GetCar()
    {
        return GetCar();
    }

    MyCar GetCar()
    {
    }
}