oop - Why can't I declare C# methods virtual and static?

Question

I have a helper class that is just a bunch of static methods and would like to subclass the helper class. Some behavior is unique depending on the subclass so I would like to call a virtual method from the base class, but since all the methods are static I can't create a plain virtual method (need object reference in order to access virtual method).

Is there any way around this? I guess I could use a singleton.. HelperClass.Instance.HelperMethod() isn't so much worse than HelperClass.HelperMethod(). Brownie points for anyone that can point out some languages that support virtual static methods.

Edit: OK yeah I'm crazy. Google search results had me thinking I wasn't for a bit there.

Answer 1

I don't think you are crazy. You just want to use what is impossible currently in .NET.

Your request for virtual static method would have so much sense if we are talking about generics. For example my future request for CLR designers is to allow me to write intereface like this:

public interface ISumable<T>
{
  static T Add(T left, T right);
}

and use it like this:

public T Aggregate<T>(T left, T right) where T : ISumable<T>
{
  return T.Add(left, right);
}

But it's impossible right now, so I'm doing it like this:

    public static class Static<T> where T : new()
    {
      public static T Value = new T();
    }

    public interface ISumable<T>
    {
      T Add(T left, T right);
    }

    public T Aggregate<T>(T left, T right) where T : ISumable<T>, new()
    {
      return Static<T>.Value.Add(left, right);
    }