public UserDto GetUser(string email)
        {
            if (!ValidationUtil.IsValidEmail(email))
            {
                throw new ArgumentException("Must be a properly formatted email", nameof(email));
            }
            UserDto toReturn = null;

            toReturn = Users?.FirstOrDefault(user => user?.Email == email);
            return(toReturn);
        }
        public override ValidationResult Validate(object value, System.Globalization.CultureInfo cultureInfo)
        {
            ValidationResult result = new ValidationResult(true, null);

            this.email = (value ?? string.Empty).ToString();
            if (this.email == null || string.IsNullOrWhiteSpace(this.email))
            {
                result = new ValidationResult(false, "Email不能为空!");
            }
            else
            {
                if (!ValidationUtil.IsValidEmail(this.email))
                {
                    result = new ValidationResult(false, "Email格式不正确,请重新输入!");
                }
            }
            return(result);
        }
        public bool AreCredentialsValid(string email, string password)
        {
            bool toReturn = false;

            if (!ValidationUtil.IsValidEmail(email))
            {
                throw new ArgumentException("Must be a properly formatted email", nameof(email));
            }
            if (password == null)
            {
                new ArgumentNullException(nameof(password));
            }
            UserDto user = this.GetUser(email);

            if (user?.Email == email && user?.Password == password)
            {
                toReturn = true;
            }
            return(toReturn);
        }