New Features in C# 2.0—Collection Interfaces: What just happened?

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What just happened?

The Pilgrim class changed just enough to implement the generic IComparable interface. The linked list didn’t change at all, but the Node class did undergo some changes to support the sorted list.

First, the Node class was marked to implement IComparable and was constrained to hold only objects that themselves implement IComparable:

public class Node<T> : IComparable<Node<T>> 
   where T:IComparable<T>

Second, Node added a reference to the previous node, in addition to the next node (making this a doubly linked list):

private Node<T> next = null;
private Node<T> prev = null;

The Node class must implement CompareTo and Equals. These are simple to implement because the constraint ensures that the data you are comparing also implements IComparable:

public int CompareTo(Node<T> rhs)
{
  // this works because of the constraint
  data.CompareTo(rhs.data);
}