Generics Warning T has same name as type from other type

Question

Given the following

public class Service<T> : IService<T>
{
        Repository<T> _repository = new Repository<T>();
        public T Get<T>(int id)
        {
            return _repository.Get<T>(id);
        }
}
public interface IService<T>
{
        T Get<T>(int id);
}

I get the following warning

Type parameter 'T' has the same name as the type parameter from outer type 'Services.IService'

I am not sure what the issue is with this, why does it care if my return type is the same as the type I am telling the class to be. Am I missing something here?

Answer 1

You'd want this instead:

public class Service<T> : IService<T>
{
        Repository<T> _repository = new Repository<T>();
        public T Get(int id)
        {
            return _repository.Get<T>(id);
        }
}

public interface IService<T>
{
        T Get(int id);
}

Basically in you're code you're trying to define Get<T>(). When you put that generic definition, you're saying it's specific to that method, not the whole class.

Answer 2

You can leave out the <T> in the declaration of Get methods. You are not introducing a new Type Parameter for the Get method which <T> says. The fact that you return a T is enough.

I think this will work:

public class Service<T> : IService<T>
{
        Repository<T> _repository = new Repository<T>();
        public T Get(int id)
        {
            return _repository.Get(id);
        }
}
public interface IService<T>
{
        T Get(int id);
}

You can create a generic method in both generic and non-generic classes.

public class Foo
{
  public T Get<T>(int a)
  {
  }
}

You could also do this in a generic class, but over a different type.

 public class Foo<T>
 {
    public S Get<S>(int a)
    {
    }
 }