Whidbey C# Generics/Iterators Question

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From: Kamen Yotov (kamen_at_yotov.org)
Date: 02/08/04 

Date: Sun, 8 Feb 2004 02:26:50 -0500

Hello,
I got my hands on the PDC preview version of whidbey and I think I managed
to break the compiler/runtime with my first Generics/Iterators attempt. The
reason I am posting it here is that I might be wrong, in which case, please
correct me!

The following program prints garbade instead the intended 5,6,1. I think it
is printing the integer values of the pointers which represent some
references... Any ideas?

using System;
using System.Collections.Generic;

namespace test2
{
 class List<T>: IEnumerable<T>, IEnumerable<ListNode<T>>
 {
  protected ListNode<T> _head;
  protected ListNode<T> _last;

  public List ()
  {
  }

  public void Add (T _value)
  {
   if (_head == null)
    _head = _last = new ListNode<T>(_value, null);
   else
    _last = _last.Next = new ListNode<T>(_value, null);
  }

  IEnumerator<T> IEnumerable<T>.GetEnumerator()
  {
   for (ListNode<T> _current = _head; _current != null; _current =
_current.Next)
    yield _current.Value;

   /*
   foreach (ListNode<T> n in (IEnumerable<ListNode<T>>)this)
    yield n.Value;
   */
  }

  IEnumerator<ListNode<T>> IEnumerable<ListNode<T>>.GetEnumerator()
  {
   for (ListNode<T> _current = _head; _current != null; _current =
_current.Next)
    yield _current;
  }
 }

 class ListNode<T>
 {
  protected T _value;
  protected ListNode<T> _next;

  public ListNode (T _value, ListNode<T> _next)
  {
   Value = _value;
   Next = _next;
  }

  public T Value
  {
   get
   {
    return _value;
   }
   set
   {
    _value = value;
   }
  }

  public ListNode<T> Next
  {
   get
   {
    return _next;
   }
   set
   {
    _next = value;
   }
  }
 }

 class Class1
 {
  [STAThread]
  static void Main(string[] args)
  {
   List<int> l = new List<int>();

   l.Add(5);
   l.Add(6);
   l.Add(1);

   foreach (int q in (IEnumerable<int>)l)
    Console.WriteLine(q);
  }
 }
}

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