public bool IsValid()
 {
     return(Name.All(kvp => kvp.Value == false) &&
            Surname.All(kvp => kvp.Value == false) &&
            Login.All(kvp => kvp.Value == false) &&
            Email.All(kvp => kvp.Value == false) &&
            Password.All(kvp => kvp.Value == false));
 }
        private bool IsInputValid()
        {
            this.ErrorsList.Clear();
            bool ForenameValid = false, SurnameValid = false, EmailAddressValid = false, PasswordValid = false, PasswordsMatch = false;

            if (!String.IsNullOrEmpty(Forename) && Forename.All(Char.IsLetter))
            {
                ForenameValid = true;
            }
            else
            {
                this.ErrorsList.Add("The forename you entered was illegal.");
            }

            if (!String.IsNullOrEmpty(Surname) && Surname.All(Char.IsLetter))
            {
                SurnameValid = true;
            }
            else
            {
                this.ErrorsList.Add("The surname you entered was illegal.");
            }

            if (!String.IsNullOrEmpty(EmailAddress) && (EmailAddress.Length > 5 && EmailAddress.Length < 70))
            {
                EmailAddressValid = true;
            }
            else
            {
                this.ErrorsList.Add("The email address you entered was invalid.");
            }

            if (Password != null && ReEnterPassword != null)
            {
                if (Password.Length >= 6)
                {
                    PasswordValid = true;
                }
                else
                {
                    this.ErrorsList.Add("The password you entered was too short. Make sure it's longer than 6 characters.");
                }

                if (Core.IsEqualTo(Password, ReEnterPassword))
                {
                    PasswordsMatch = true;
                }
                else
                {
                    this.ErrorsList.Add("The passwords you entered don't match.");
                }
            }
            else
            {
                this.ErrorsList.Add("You need to enter a password in both fields.");
            }

            bool valid = ForenameValid && SurnameValid && EmailAddressValid && PasswordValid && PasswordsMatch;

            this.Errors = !valid;
            return(valid);
        }