ASP.NET MVC Check if User has already posted in this table - asp.net-mvc

Question

I'm gonna cut to the chase.
I'm creating a Survey platform, it has 3 models.
Model Survey, it has Many SurveyQuestion which has many SurveyAnswer.
(I can insert all of the values of these models but I dont think it is needed)
public class SurveyAnswer
{
[Key]
public int Id { get; set; }
public string Value { get; set; }
public string SubmittedBy { get; set; }
public int SurveyId { get; set; }
public int QuestionId { get; set; }
public virtual Survey Survey { get; set; }
public virtual SurveyQuestion Question { get; set; }
public string Comment { get; set; }
}
Now a problem I'm having is once someone created a survey and another person is starting it, he answers and that's it. How do I show that the next time he comes to an index page? How do I show that "you already submitted this survey"? Do I do that in Controller or in View? I would prefer to that in this action currently (it's a menu for all ongoing surveys).
[HttpGet]
public ActionResult Menu()
{
var survey = Mapper.Map<IEnumerable<Survey>, IEnumerable<SurveyViewModel>>(_unitOfWork.SurveyRepository.Get());
return View(survey.ToList());
}

Answer 1

Put all your validation rules to your AbstractValidator class.
[Validator(typeof(SurveyAnswerValidator))]
public class SurveyAnswer{
[Key]
public int Id { get; set; }
public string Value { get; set; }
public string SubmittedBy { get; set; }
public int SurveyId { get; set; }
public int QuestionId { get; set; }
public virtual Survey Survey { get; set; }
public virtual SurveyQuestion Question { get; set; }
public string Comment { get; set; }
}
public class SurveyAnswerValidator : AbstractValidator<SurveyAnswer>
{
public SurveyAnswerValidator()
{
//list your rules
RuleFor(x => x.SubmittedBy).Must(BeUnique).WithMessage("Already
submitted this survey");
}
private bool BeUnique(string submittedBy)
{
if(_context.SurveyAnswers.
FirstOrDefault(x => x.SubmittedBy == submittedBy) == null){
return true;
}
else{
return false;
}
}
}
If you want to check uniqueness in ViewModel you can use Remote.
public class SurveyAnswerVM{
[Key]
public int Id { get; set; }
public string Value { get; set; }
[Remote("HasSubmitted", "ControllerName")]
public string SubmittedBy { get; set; }
public int SurveyId { get; set; }
public int QuestionId { get; set; }
public virtual Survey Survey { get; set; }
public virtual SurveyQuestion Question { get; set; }
public string Comment { get; set; }
}
Where HasSubmitted is a method you may create in controller to return true if the user has submitted.
RemoteAttribute
https://msdn.microsoft.com/en-us/library/gg508808(VS.98).aspx

Answer 2

The best solution by vahdet (suggested in comments)
[Index("IX_AnswerQuestion", 2, IsUnique = true)]
[StringLength(36)]
public string SubmittedBy { get; set; }
public int SurveyId { get; set; }
[Index("IX_AnswerQuestion", 1, IsUnique = true)]
public int QuestionId { get; set; }