.NET截取指定長度的漢字超出部分用“···”代替

/// <summary>
/// 將指定的字元串按指定的長度剪切
/// </summary>
/// <param name="oldStr">需要剪切的字元串</param>
/// <param name="maxLength">需要字元串的最大的長度</param>
/// <param name="endWith">超過長度的尾碼</param>
/// <returns>如果超過長度，返回截取的字元串加上尾碼；否則返回原字元串</returns>
    public static string StringTruncate(string oldStr, int maxLength, string endWith)
    {
        if (string.IsNullOrEmpty(oldStr))
            return oldStr + endWith;
        if (maxLength < 1)
            throw new Exception("返回的字元串長度必須大於[0]");
        if (oldStr.Length > maxLength)
        {
            string strTmp = oldStr.Substring(0, maxLength);
            if (string.IsNullOrEmpty(endWith))
                return oldStr;
            else
                return  strTmp + endWith;
        }
        return oldStr;
    }
}