C#/asp.net文本长度判断、判断邮件格式、判断下拉菜单、判断是否为数字

/// <summary>
        /// 文本长度判断
        /// </summary>
        public static bool TextLength(int min, int max, string s)
        {
            if (s.Length < min || s.Length > max)
            {
                return false;
            }
            else
            {
                return true;
            }
        }

        /// <summary>
        /// 判断邮件格式
        /// </summary>
        public static bool IsEmail(string inputEmail)
        {
            string strRegex = @"^([a-zA-Z0-9_\-\.]+)@((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.)|(([a-zA-Z0-9\-]+\.)+))([a-zA-Z]{2,4}|[0-9]{1,3})(\]?)$";
            Regex re = new Regex(strRegex);
            if (re.IsMatch(inputEmail))
                return (true);
            else
                return (false);
        }

        /// <summary>
        /// 判断下拉菜单
        /// </summary>
        public static bool CheckDropDownList(DropDownList list)
        {
            if (list.SelectedIndex < 1)
                return false;
            else
                return true;
        }
       /// <summary>
       /// 判断是否为数字
       /// </summary>
       /// <param name="itemValue"></param>
       /// <returns></returns>

        public static bool IsNumber(string itemValue)
        {

            string regExValue = "^(-?[0-9]*[.]*[0-9]{0,3})$"; 
            Regex regex = new Regex(regExValue);
            if (regex.IsMatch(itemValue))
                return true;
            else
                return false;

        }

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