How do you cast an generic class into an generic class of object?

Question

let's say that you have 2 classes:

public abstract class Foo<T> {
    public abstract T DoSomething();
}

public class FooInt : Foo<int> {
    public override int DoSomething() {
        return 42;
    }
}

I want to cast FooInt into Foo<object>. And it is hard to restructure the code because I have a List<Foo<object>> that stores all the Foo class instances. And I do want to keep the overrides of FooInt.

---

I have tried this:

public static implicit operator Foo<object>(Foo<T> field) { return (Foo<object>)field; }

But I got an Overflow Exception, because it called itself. Then I tried this:

public static implicit operator Foo<object>(Foo<T> field) { return (field as Foo<object>)!; }

But that returned null. And I tried this:

public static implicit operator Foo<object>(Foo<T> field) { return (Foo<object>)(object)field;}

But that gave an Invalid Cast Exception. And I also tried removing the cast but that didn't work either.

Answer 1

@Fildor comments , like this

public interface IFoo
{
    void DoSome();
}

public abstract class Foo<T> : IFoo
{
    public abstract T DoSomething();
    public void DoSome()
    {
        DoSomething();
    }
}

public class FooInt : Foo<int>
{
    public override int DoSomething()
    {
        return 42;
    }
}
public class FooDouble : Foo<double>
{
    public override double DoSomething()
    {
        return 42.0;
    }
}


List<IFoo> list = new List<IFoo>()
   {
       new FooInt(),
       new FooDouble()
   };
 foreach (var item in list)
 {
     item.DoSome();
 }