C#使用迭代法实现Fibnaci数列

public List<int> BaseNumbers = new List<int> { 1, 1, 2, 3, 5, 8 };
public int GetFibnaceNumber(List<int> baseNumbers, int len)
{
  if (len <= 2)
  {
 return 1;
  }
  else if ((len - 1) <= BaseNumbers.Count)
  {
 len = len - 1;
 return BaseNumbers[len - 1] + BaseNumbers[len - 2];
  }
  else
  {
 int BaseMaxIndex = BaseNumbers.Count;
 BaseNumbers.Add(BaseNumbers[BaseMaxIndex - 1] + BaseNumbers[BaseMaxIndex - 2]);
 return GetFibnaceNumber(BaseNumbers, len);
  }
}