C#•2y ago

Calling a static abstract method without a generic type [Answered]

If I have this code with a static abstract member Bar in the interface IFoo, is there any way (besides reflection) to call Bar on an instance of IFoo without the explicit type of the instance?

IFoo f = GetFoo();
f.Bar(); // ???

static IFoo GetFoo() =>
  new Foo();

interface IFoo {
  static abstract void Bar();
}
class Foo : IFoo {
  public static void Bar() =>
    Console.WriteLine("bar");
}

IFoo f = GetFoo();
f.Bar(); // ???

static IFoo GetFoo() =>
  new Foo();

interface IFoo {
  static abstract void Bar();
}
class Foo : IFoo {
  public static void Bar() =>
    Console.WriteLine("bar");
}

12 Replies

Thinker•2y ago

I know it'd be trivial to do this using reflection, but like... it's reflection

var type = f.GetType();
var map = type.GetInterfaceMap(typeof(IFoo));
var bar = map.TargetMethods.First(m => m.Name == "Bar");
bar.Invoke(null, Array.Empty<object?>());

var type = f.GetType();
var map = type.GetInterfaceMap(typeof(IFoo));
var bar = map.TargetMethods.First(m => m.Name == "Bar");
bar.Invoke(null, Array.Empty<object?>());

Like Bar is there, it has to exist in the type of f, but it's inaccessible without an explicit type, which is impossible to get with just an instance of something.

333fred•2y ago

Use an instance method

Thinker•2y ago

hmm I mean that doesn't really solve the issue

333fred•2y ago

Well, you're trying to use a static method like an instance method here It doesn't seem like a realistic scenario

333fred•2y ago

https://tenor.com/view/rethink-your-life-obiwan-star-wars-bar-gif-10722441

Tenor

333fred•2y ago

My suggestion is to rethink what you're trying to accomplish

Thinker•2y ago

Well I mean, this isn't a practical example. The only real use is that methods which call static abstract members have to have type parameters, which can become an issue if you either only have the interface type or if the type cannot be inferred and you have to manually write out some big declaration. Though I agree that yes this is barely practical anyway

333fred•2y ago

The only real use is that methods which call static abstract members have to have type parameters

yes If you don't have this, you're using a square peg to go in a round hole

Thinker•2y ago

It's still slightly annoying

333fred•2y ago

It should be

Thinker•2y ago

I mean... fair, there's a clear distinction between static and instance, but this still to me feels like one of the major drawbacks of static abstracts

Accord•2y ago

✅ This post has been marked as answered!

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Calling a static abstract method without a generic type [Answered]