///   summary>
    ///   將指定字符串按指定長度進行剪切，
    ///   /summary>
    ///   param   name= "oldStr "> 需要截斷的字符串 /param>
    ///   param   name= "maxLength "> 字符串的最大長度 /param>
    ///   param   name= "endWith "> 超過長度的后綴 /param>
    ///   returns> 如果超過長度，返回截斷后的新字符串加上后綴，否則，返回原字符串 /returns>
    public static string StringTruncat(string oldStr, int maxLength, string endWith)
    {
        if (string.IsNullOrEmpty(oldStr))
            //   throw   new   NullReferenceException( "原字符串不能為空 ");
            return oldStr + endWith;
        if (maxLength 1)
            throw new Exception("返回的字符串長度必須大于[0] ");
        if (oldStr.Length > maxLength)
        {
            string strTmp = oldStr.Substring(0, maxLength);
            if (string.IsNullOrEmpty(endWith))
                return strTmp;
            else
                return strTmp + endWith;
        }
        return oldStr;
    }