Just as in generic classes, it is useful to define generic interfaces. It's useful to define generic interfaces for collections such as linked lists.

In this example, we are defining a generic interface that requires T to be a reference type.

// File: GenericInterfaces.cs
using System;

public interface INode<T> where T:class
{
    string Value
    {
        get;
    }
    T Next
    {
        get;
    }
}

public class PersonNode : INode<PersonNode>
{
    private string name;
    private PersonNode next;

    public PersonNode(string name, PersonNode next)
    {
        this.name = name;
        this.next = next;
    }

    public string Value
    {
        get
        {
            return name;
        }
    }

    public PersonNode Next
    {
        get
        {
            return next;
        }
    }
}

public class Program
{
    static void Main()
    {
        PersonNode danNode = new PersonNode("dan", null);
        PersonNode sabetNode = new PersonNode("sabet", danNode);
        PersonNode mikeNode = new PersonNode("mike", sabetNode);

        PersonNode node = mikeNode;

        while (node != null)
        {
            Console.WriteLine(node.Value);
            node = node.Next;
        }

        Console.ReadLine();
    }
}