Looping generic type in c#

Question

I need to make the graph and I want to the edges and the vertices to be generic type

public interface IVertex<TVertex, TEdge>
        where TVertex : IVertex<?>
        where TEdge : IEdge<?>
{
    bool AddEdge(TEdge e);
    TEdge FindEdge(TVertex v);
}

public interface IEdge<TVertex> where TVertex : IVertex<?>
{
    TVertex From { get; }
}

But, the edge required the vertex type and the vertex required the edge type What should I do?

Answer 1

I think you're making it more complicated then it needs to be.
Would something like this work?

public interface IVertex<T>
{
    bool AddEdge(IEdge<T> e);
    IEdge<T> FindEdge(IVertex<T> v);
}

public interface IEdge<T>
{
    IVertex<T> From { get; }
}

Answer 2

While it's arguable whether or not it's actually a good idea, there's nothing the compiler minds about such "looping" definitions:

interface IVertex<TVertex, TEdge> where TVertex : IVertex<TVertex,TEdge>
                                  where TEdge : IEdge<TVertex,TEdge>
{

}

interface IEdge<TVertex, TEdge> where TVertex : IVertex<TVertex, TEdge>
                                where TEdge : IEdge<TVertex, TEdge>
{

}

Then you can write, for example:

class FooVertex : IVertex<FooVertex,BarEdge>
{

}

class BarEdge : IEdge<FooVertex,BarEdge>
{

}