验证、截取、生成 字符

 public static class Tool
    {
        /// <summary>
        /// 获取随机字母
        /// </summary>
        /// <param name="length"></param>
        /// <returns></returns>
        public static string GetRandomCode(int length)
        {
            var rom = new Random(Guid.NewGuid().GetHashCode());
            char[] allcheckRandom ={'A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P','Q','R','S','T','U','V','W',
                'X','Y','Z','a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q',
                'r','s','t','u','v','w','x','y','z','2','3','4','5','6','7','8','9'};
            var randomcode = "";
            for (var i = 0; i < length; i++)
            {
                randomcode += allcheckRandom[rom.Next(allcheckRandom.Length)];
            }
            return randomcode;
        }

        /// <summary>
        /// 获取随机字母
        /// </summary>
        /// <param name="length"></param>
        /// <returns></returns>
        public static string GetRandomNum(int length)
        {
            var rom = new Random(Guid.NewGuid().GetHashCode());
            char[] allcheckRandom = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9' };
            var randomcode = "";
            for (var i = 0; i < length; i++)
            {
                randomcode += allcheckRandom[rom.Next(allcheckRandom.Length)];
            }
            return randomcode;
        }

        /// <summary>
        /// 获取时间戳字符串
        /// </summary>
        /// <param name="time"></param>
        /// <param name="length"></param>
        /// <returns></returns>
        public static string GetTimeStamp(System.DateTime time, int length = 13)
        {
            long ts = ConvertDateTimeToInt(time);
            return ts.ToString().Substring(0, length);
        }

        public static long ConvertDateTimeToInt(System.DateTime time)
        {
            System.DateTime startTime = TimeZone.CurrentTimeZone.ToLocalTime(new System.DateTime(1970, 1, 1, 0, 0, 0, 0));
            long t = (time.Ticks - startTime.Ticks) / 10000;   //除10000调整为13位      
            return t;
        }
        /// <summary>
        /// 效验是否为身份证
        /// </summary>
        /// <param name="num"></param>
        /// <returns></returns>
        public static bool IsValidIdentity(string num)
        {
            num = num.ToUpper();
            //身份证号码为15位或者18位，15位时全为数字，18位前17位为数字，最后一位是校验位，可能为数字或字符X。 
            Regex regex = new Regex(@"^[1-9]\d{7}((0\d)|(1[0-2]))(([0|1|2]\d)|3[0-1])\d{3}$|(^[1-9]\d{5}[1-9]\d{3}((0\d)|(1[0-2]))(([0|1|2]\d)|3[0-1])\d{3}([0-9]|X)$)");
            if (!regex.IsMatch(num))
            { return false; }
            //校验位按照ISO 7064:1983.MOD 11-2的规定生成，X可以认为是数字10。   
            //下面分别分析出生日期和校验位
            var len = num.Length;
            var arrInt = new int[] { 7, 9, 10, 5, 8, 4, 2, 1, 6, 3, 7, 9, 10, 5, 8, 4, 2 };
            var arrCh = new string[] { "1", "0", "X", "9", "8", "7", "6", "5", "4", "3", "2" };
            var nTemp = 0;
            if (len == 15)
            {
                //将15位身份证转成18位   
                //校验位按照ISO 7064:1983.MOD 11-2的规定生成，X可以认为是数字10。   
                nTemp = 0;
                num = num.Substring(0, 6) + "19" + num.Substring(6, len - 6);
                for (var i = 0; i < 17; i++)
                {
                    nTemp += int.Parse(num.Substring(i, 1)) * arrInt[i];
                }
                num += arrCh[nTemp % 11];
            }
            else
            {
                //检验18位身份证的校验码是否正确。   
                //校验位按照ISO 7064:1983.MOD 11-2的规定生成，X可以认为是数字10。   
                nTemp = 0;
                for (var i = 0; i < 17; i++)
                {
                    nTemp += int.Parse(num.Substring(i, 1)) * arrInt[i];
                }
                var valnum = arrCh[nTemp % 11];
                if (valnum != num.Substring(17, 1))
                { return false; }
            }
            var aCity = new Dictionary<int, string>
            {
                {11, "北京"}, {12, "天津"}, {13, "河北"}, {14, "山西"}, {15, "内蒙古"}, {21, "辽宁"}, {22, "吉林"}, {23, "黑龙江"},
                {31, "上海"}, {32, "江苏"}, {33, "浙江"}, {34, "安徽"}, {35, "福建"}, {36, "江西"}, {37, "山东"},
                {41, "河南"}, {42, "湖北"}, {43, "湖南"}, {44, "广东"}, {45, "广西"}, {46, "海南"},
                {50, "重庆"}, {51, "四川"}, {52, "贵州"}, {53, "云南"}, {54, "西藏"},
                {61, "陕西"}, {62, "甘肃"}, {63, "青海"}, {64, "宁夏"}, {65, "新疆"}, {71, "台湾"}, {81, "香港"}, {82, "澳门"}, {91, "国外"}
            };
            var sId = num.Replace("X", "a");
            var iSum = 0;
            if (!aCity.ContainsKey(int.Parse(sId.Substring(0, 2))))
            { return false; }
            for (var i = 17; i >= 0; i--) { iSum += Convert.ToInt32(Math.Pow(2.0, Convert.ToDouble(i)) % 11) * Convert.ToInt32(sId.Substring(17 - i, 1), 16); }
            return iSum % 11 == 1;
        }

        /// <summary>
        /// 截取出身年月日
        /// </summary>
        /// <param name="IDCard">身份证号</param>
        /// <returns></returns>
        public static string GetDate(string IDCard)
        {
            string BirthDay = " ";
            string strYear;
            string strMonth;
            string strDay;
            if (IDCard.Length == 15)
            {
                strYear = IDCard.Substring(6, 2);
                strMonth = IDCard.Substring(8, 2);
                strDay = IDCard.Substring(10, 2);
                BirthDay = "19" + strYear + "- " + strMonth + "- " + strDay;
            }
            if (IDCard.Length == 18)
            {
                strYear = IDCard.Substring(6, 4);
                strMonth = IDCard.Substring(10, 2);
                strDay = IDCard.Substring(12, 2);
                BirthDay = strYear + "- " + strMonth + "- " + strDay;
            }
            return BirthDay;
        }
        /// <summary>
        /// 效验是否为邮件地址，中间必须含有@符号，例：sina@sina.com
        /// </summary>
        /// <param name="strIn"></param>
        /// <returns></returns>
        public static bool IsValidEmail(string strIn)
        {
            Regex regex = new Regex(@"^[\w-]+(\.[\w-]+)*@[\w-]+(\.[\w-]+)+$");
            return regex.IsMatch(strIn);
        }
        /// <summary>
        /// 效验是否为手机号码，11位的整数数字，例：158,8888,8888
        /// </summary>
        /// <param name="strIn"></param>
        /// <returns></returns>
        public static bool IsValidMobile(string strIn)
        {
            Regex regex = new Regex(@"^1[3|4|6|9|5|8|7][0-9]\d{8}$");
            return regex.IsMatch(strIn);
        }

        /// <summary>
        /// 效验固定电话
        /// </summary>
        /// <param name="strIn"></param>
        /// <returns></returns>
        public static bool IsValidTelephone(string strIn)
        {
            Regex regex = new Regex(@"^(\d{3,4}-)?\d{7,8}$");
            return regex.IsMatch(strIn);
        }

        /// <summary>
        /// 获取客户端IP地址（无视代理）
        /// </summary>
        /// <returns>若失败则返回回送地址</returns>
        public static string GetHostAddress()
        {
            string userHostAddress = HttpContext.Current.Request.UserHostAddress;

            if (string.IsNullOrEmpty(userHostAddress))
            {
                userHostAddress = HttpContext.Current.Request.ServerVariables["REMOTE_ADDR"];
            }

            //最后判断获取是否成功，并检查IP地址的格式（检查其格式非常重要）
            if (!string.IsNullOrEmpty(userHostAddress) && IsIP(userHostAddress))
            {
                return userHostAddress;
            }
            return "127.0.0.1";
        }

        /// <summary>
        /// 检查IP地址格式
        /// </summary>
        /// <param name="ip"></param>
        /// <returns></returns>
        public static bool IsIP(string ip)
        {
            return Regex.IsMatch(ip, @"^((2[0-4]\d|25[0-5]|[01]?\d\d?)\.){3}(2[0-4]\d|25[0-5]|[01]?\d\d?)$");
        }

    }