截取指定长度中英文字符串

最近在做项目时,碰到含有中英文混在一起的字符串,而存入数据库(DB2)又是限定长度的,找到了一个比较好的截取指定长度中英文字符方法:
#region 截取指定长度中英文字符串

  /// <summary>
  /// 截取指定长度中英文字符串
  /// </summary>
  /// <param name="stringToSub">字符串</param>
  /// <param name="length">截取长度</param>
  /// <returns>返回字符串</returns>
  public static string FormatString(string stringToSub, int length)
  {
   Regex regex = new Regex("[\u4e00-\u9fa5]+", RegexOptions.Compiled);
   char[] stringChar = stringToSub.ToCharArray();
   StringBuilder sb = new StringBuilder();
   int nLength = 0;

   for (int i = 0; i < stringChar.Length; i++)
   {
    if (nLength == length - 1)
    {
     if (regex.IsMatch((stringChar[i]).ToString()))
     {
      break;
     }
    }

    if (regex.IsMatch((stringChar[i]).ToString()))
    {
     sb.Append(stringChar[i]);
     nLength += 2;
    }
    else
    {
     sb.Append(stringChar[i]);
     nLength = nLength + 1;
    }

    if (nLength >= length)
    {
     break;
    }
   }

   return sb.ToString();
  }

  #endregion