Simple number sequence.

NumberSequence.cs

public class NumberSequence : IEnumerable<int>
{
  private readonly int _startValue;
  private readonly int _increment;

  public NumberSequence(int startValue, int increment)
  {
    _startValue = startValue;
    _increment = increment;
  }

  public IEnumerator<int> GetEnumerator()
  {
    return new NumberEnumerator(_startValue, _increment);
  }

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

public class NumberEnumerator : IEnumerator<int>, 
  IComparable<NumberEnumerator>
{
  private readonly int _increment;
  private int _currentValue;

  public NumberEnumerator(int startValue, int increment)
  {
    _currentValue = startValue;
    _increment = increment;
  }

  public bool MoveNext()
  {
    _currentValue += _increment;
    return true;
  }

  public int Current
  {
    get { return _currentValue; }
  }

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

  public void Dispose() { }

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

  public int CompareTo(NumberEnumerator other)
  {
    return Current.CompareTo(other.Current);
  }
}