Question

I was mildly surprised when the compiler complained about this:

public class UsefulClass
{
    public const String RatingName = @"Ratings\rating";
}

public class OtherClass
{
    public void SomeFunc()
    {
        UsefulClass useful = new UsefulClass();
        String rating = useful.RatingName;
    }
}

Compiler says, “Static member cannot be accessed with an instance reference; qualify it with a type name instead”

This isn’t a problem, String rating = UsefulClass.RatingName; works fine. I’m just curious what the thinking is behind this? I have an instance of a public class with a public constant on it, why can’t I get the data this way?

Answer 1

Because constants just aren’t instance members; they’re statically bound to their respective types. In the same way you can’t invoke static methods using instances, you can’t access class constants using instances.

If you need to get a constant off an instance without knowing its type first-hand, I suppose you could do it with reflection based on its type.

If you’re trying to add a member that can’t be modified but pertains to instances, you probably want read-only fields or properties instead.