How to implement the override methods of Equals and GetHashCode in a class that implements IProxyGenerationHook in Castle.Core?

Question

Reading the Castle.Core documentation, in this link, they recommend that always overriding the Equals and GetHashCode methods of the classes that implement IProxyGenerationHook.

I have a class called MiHook that implements such interface, but this class doesn't have state. So, my question is, how should I override those two methods if I have a stateless class?

public class MiHook : IProxyGenerationHook {
    public void MethodsInspected() { }

    public void NonProxyableMemberNotification(Type type, MemberInfo memberInfo) { }

    public bool ShouldInterceptMethod(Type type, MethodInfo methodInfo) {
        return methodInfo.Name == nameof(IFoo.Bar);
    }

    // Should I implement both methods like this?
    public override bool Equals(object? obj) => base.Equals(obj);
    public override int GetHashCode() => base.GetHashCode();
}

Answer 1

I'm not sure what do you mean by stateless class - do you mean that it doesn't have any fields? what is a stateless class?

Base implementation in your example is as good as not overriding at all. You need to ask yourself a question:

What makes two objects of type MiHook equal?

Judging by your implementation of ShouldInterceptMethod it is the Type(IFoo.Bar). If that's the case, I would go for a IFoo.Bar - "dependent" override:

   public class MiHook : IProxyGenerationHook
    {
        public void MethodsInspected() { }
        public void NonProxyableMemberNotification(Type type, MemberInfo memberInfo) { }
        public bool ShouldInterceptMethod(Type type, MethodInfo methodInfo)
        {
            return methodInfo.Name == nameof(IFoo.Bar);
        }
        public override bool Equals(object obj)
        {
            if (obj == null || obj.GetType() != this.GetType()) return false;
            return obj.GetHashCode() == this.GetHashCode();
        }
        public override int GetHashCode() => typeof(IFoo.Bar).GetHashCode();
    }

To test it:

var mh1 = new MiHook<Foo.Bar>();
var mh2 = new MiHook<Foo.Bar>();
Console.WriteLine(mh1.Equals(mh2)); //True
//your implementation returns False

Answer 2

In the Glimpse project the IProxyGenerationHook is also overridden. Although they still have a private field that is used to override GetHashCode and Equals:

private IEnumerable<IAlternateMethod> methodImplementations;

Here is the link to the source file that contains the methods GetHashCode and Equals.

Maybe it is useful as source of inspiration.