是否可以在c＃中使用“隐式”泛型类型参数

Question

I have a generic type:

public class Source<T> where T : ISomeInterface<X> //...

Now, my problem is, I really don't want to modify Source<T> to Source<T,X> , but I want to use X inside Source.
Is it possible in any way?

Answer 1

No, there's no way of expressing that. If you want to be able to refer to X within Source , it has to be a type parameter.

Bear in mind that T could implement (say) ISomeInterface<string> and ISomeInterface<int> . What would X be in that case?

Answer 2

If you're using a generic type, you're telling the compiler that you're going to provide the actual type when creating a concrete instance. With your code, if you tried to do a

Source<string> s = new Source<string>();

the compiler would know that T is actually a string in the class, but you're not giving the compiler any info on what X would be. However, depending on what you want to do, you may be able to use a "has a" relationship with Interface with a naked type constraint instead of using inheritance. The following code does compile, for instance:

public interface ISomeInterface<X> 
{
    void SomeMethod(X someparam);
}    

public class Source<T> 
{
    public void MyMethod<X>(ISomeInterface<X> someConcreteInstance) where X:T
    {

    }        
}