semi-private inner-class

Question

I'm implementing a union-find data structure in C#. The elements must extend the Element inner-class, but I'd like to to keep the fields in that class private to the outside world. They need to be public to the direct outer-class, however. The folloowing code does not compile due to "inconsistent accessibility":

class DisjointSetForrests<T> where T : DisjointSetForrests<T>.Element {

    private class PrivateElement {
        public Element p;
        public int     rank;
    }

    public class Element : PrivateElement {
    }

    public void MakeSet(T x) {
        x.p    = x;
        x.rank = 0;
    }

    public T FindSet(T x) {
        if (x != x.p) x.p = FindSet(x);
        return (T)x.p;
    }

    public void Union(T x, T y) {
        Link(FindSet(x), FindSet(y));
    }

    public void Link(T x, T y) {
        if (x.rank > y.rank) {
            y.p = x;
        } else {
            x.p = y;
            if (x.rank == y.rank) y.rank++;
        }
    }
}

Is there a way to achieve what I want, or should I accept the fields in Element being public?

Answer 1

It's not possible to keep them only public to the outer class. The question is why do you need to keep them public? If you creating a library you could use internal.