I just want to confirm what I've understood about Generics in C#. This has come up in a couple code bases I've worked in where a generic base class is used to create type-safe derived instances. A very simple example of what I'm talking about,
public class SomeClass<T>
{
public virtual void SomeMethod(){ }
}
public class DeriveFrom :SomeClass<string>
{
public override void SomeMethod()
{
base.SomeMethod();
}
}
The problem comes up when I then want to use derived instances in a polymorphic way.
public class ClientCode
{
public void DoSomethingClienty()
{
Factory factory = new Factory();
//Doesn't compile because SomeClass needs a type parameter!
SomeClass someInstance = factory.Create();
someInstance.SomeMethod();
}
}
It seems that once you introduce a Generic into an inheritance hierarchy or interface, you can no longer use that family of classes in a polymorphic way except perhaps internal to itself. Is that true?