Simple iterator for primes.

PrimeSequence.cs

public class PrimeSequence : IEnumerable<int>
{
  public IEnumerator<int> GetEnumerator()
  {
    return new SimplePrimeEnumerator();
  }

  IEnumerator IEnumerable.GetEnumerator()
  {
    return GetEnumerator();
  }
}

public class SimplePrimeEnumerator : IEnumerator<int>
{
  private readonly IEnumerator<int> _candidates = 
    new NumberSequence(1, 1).GetEnumerator();
  private IPriorityQueue<NumberEnumerator> _pq = 
    new IntervalHeap<NumberEnumerator>();

  public int Current
  {
    get { return _candidates.Current; }
  }

  public bool MoveNext()
  {
    while (true)
    {
      _candidates.MoveNext();
      int n = _candidates.Current;

      if (_pq.IsEmpty || n < _pq.FindMin().Current)
      {
        // There are no pending prime-multiples.
        // This means n is a prime!
        _pq.Add(new NumberEnumerator(n*n, n));
        return true;
      }
      do
      {
        var temp = _pq.DeleteMin();
        temp.MoveNext();
        _pq.Add(temp);
      } while (n == _pq.FindMin().Current);
    }
  }

  object IEnumerator.Current
  {
    get { return Current; }
  }

  public void Reset()
  {
    throw new NotSupportedException();
  }

  public void Dispose() {}
}