public ValidationPageViewModel()
{
UserName = new ValidatableObject <string>();
UserName.AddRule(new StringNotEmptyRule("A username is required."));
UserName.AddRule(new StringLengthRule(3, 10, "Username must be 3-10 characters."));
Email = new ValidatableObject <string>();
Email.AddRule(new StringNotEmptyRule("Email is required."));
Email.AddRule(new EmailRule("Invalid Email."));
TermsAndCondition = new ValidatableObject <bool>();
TermsAndCondition.AddRule(new IsValueTrueRule("Please accept terms and condition"));
_validationGroup = new ValidatableGroup(UserName, Email, TermsAndCondition);
CheckNameCommand = new RelayCommand(CheckName);
SubmitCommand = new AsyncCommand(SubmitAsync);
}