WEB API C# - Filter parameter validation

Question

I am trying to create an API using best practices with a simple validation by example.

public class ClientController
{
       [HttpGet]
       [Authorize] 
       public IHttpActionResult Clients([FromUri]string Initialdate,[FromUri] string finalDate)
       {
           return _clientRepository.GetClients();
       }
}


public class ClientRepository
{
        //some code that access data layer
        public IEnumerable<Client> GetClients(string initialDate,string finalDate)
        {
             //HERE IS WHAT IM LOOKING FOR
             //HERE I WANT TO VALIDATE THE DATE PARAMETER PROVIDED IN REQUEST AND RETURN 
             //VALIDATION LIST WITH ERROR DESCRIPTION IN JSON

             _daoClient.ExecuteProcedure(initialDate,finalDate);
        }
}


public class Client
{
    public int Id {get;set;}
    public string Name {get;set;}
}

So, how can i build this simple validation of parameters in request with action like a parameter filters?

I suggest not to do validation inside your repository. There are few ways you can validate check out this blog — Hasta Tamang
– Hasta Tamang, Commented Sep 17, 2019 at 15:21
You want to add attribute validation on class Client properties? — awais
– awais, Commented Sep 17, 2019 at 18:34
No, i want to validate query parameters from get method, and return in a list of Json the problems with them. Example: GetClient with invalid date, and return the error , thats why i can't use modelstate. because it is like an filter than propertie from a model. — Renan Duarte
– Renan Duarte, Commented Sep 17, 2019 at 19:41
@RenanDuarte please check my answer below, you can do like this. — awais
– awais, Commented Sep 18, 2019 at 7:58

awais · Accepted Answer · 2019-09-18 07:56:21Z

2

You have to do validate explicitly like this then:

[HttpGet]
[Authorize]
public IHttpActionResult Clients([FromUri]string Initialdate, [FromUri] string finalDate)
{
         bool isInitialDate = DateTime.TryParse(Initialdate, out DateTime tempInitialdate);
         bool isFinalDate = DateTime.TryParse(finalDate, out DateTime tempfinalDate);

         List<string> _errorMessage = new List<string>();

         if (!isInitialDate)
              _errorMessage.Add("Initial date is invalid");

         if(!isFinalDate)
             _errorMessage.Add("Final date is invalid");

         if(isInitialDate && isFinalDate)
         {
                //your business logic
                return _clientRepository.GetClients();
         }

            return Json(new { success = false, error = _errorMessage });
}

answered Sep 18, 2019 at 7:56

awais

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3 Comments

Renan Duarte Over a year ago

Nice awais, but i was thinking to abstract this validation from controller and transfer the resposability to another layer, and return erros with list of errors found or success with the information that was requested by the user.

awais Over a year ago

Dear @RenanDuarte I got your point for that you need to create an interceptor class and configure in startup.cs`` e.g.: config.MessageHandlers.Insert(0, new ApiDelegatingHandler());``` in ApiDelegatingHandler class you need to inherit public class ApiDelegatingHandler : DelegatingHandler and write your custom validation in order to achieve the above requirement. I would highly recommend using the above logic to validate at controller level.

Renan Duarte Over a year ago

Firstly, thank you for contribuition. So, can you tell me the reason to maintain the parameter validation at the ontroller level ?

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