What is the difference between "class A : B<C>" and "class A<T> : B<T> where T : C"?

Question

I am trying to create a derived class from a generic class, and I was wondering what the differences are between

public class A<T> : B<T> where T : C
{
}

and

public class A: B<C>
{
}

Inside class A there probably will be no code, since (for now) it will not behave different from class B. I only want to distinguish the two classes.

Thanks in advance.

Answer 1

Say you had a class

public class D : C
{
}

Then in your first example the below is valid.

var a = new A<D>

You can use any class for T that is ultimately derived from C.

Whereas your second code is hard coded to have B use C for the genric type parameter and is not generic.

Answer 2

It is a Constraints with generics in C#, for sample:

In

public class A<T> : B<T> where T : C
{
}

The generic T must be a C type or a child of it (what is a abstraction).

In

public class A: B<C>
{
}

The generic is C.

Answer 3

In your first example, A is a generic class, of type C. It also inherits from class B of type C.

Your second example has the following properties:

A is not a generic class. It inherits from class B of type C.

So, they are actually quite different.