字符串实际长度及其根据实际长度截取的问题

1：获取字符串实际长度

   public int StringLength(string oString)
    {
        byte[] strArray = System.Text.Encoding.Default.GetBytes(oString);
        int res = strArray.Length;
        return res;
    }

2：根据字符串的实际长度来截取

    /// <summary>
    /// 根据实际长度截取字符串
    /// </summary>
    /// <param name="str">原字符串</param>
    /// <param name="length">指定截取长度</param>
    /// <returns>返回截取后的string</returns>
    public static string GetString(string str, int length)
    {
        int i = 0, j = 0;
        foreach (char chr in str)
        {
            if ((int)chr > 127)
            {
                i += 2;
            }
            else
            {
                i++;
            }
            if (i > length)
            {
                str = str.Substring(0, j) + "...";
                break;
            }
            j++;
        }
        return str;
    }