Covariance in C# generic class

Question

C# 4.0 .NET 4.5 Silverlight 5 It seems weird that I cant find the solution so need some help please.

I have base class Base and derived class Child : Base. I have also h

Answer 1

If Foo : Bar, that doesn't mean that Some : Some. There are two ways of doing what you want. The first is to make the base-type generic such that:

Base where T : EntityObject {
    protected Helper helper;
}
Child : Base {...}

The second is to use a non-generic interface at the base-type, i.e. have

Base {
    protected IHelper helper;
}
Child : Base {...}

where in the latter case, Helper : IHelper, for some non-generic IHelper to-be-defined.

As a side-note, you might find it easier to pass the value down in the constructor rather than using a protected field.