ASP.NET MVC Remote Validation logic on Edit

Question

I have a model and an actionMethod in MVC;

public class employee
{
    [Key]
    public int id { get; set; }

    [Required]
    public string employeeID { get; set; }

    [Required]
    [Remote("doesCnicExist", "employee", AdditionalFields = "employeeID", HttpMethod = "POST", ErrorMessage = "A user with this cnic already exists. Please enter a different cnic.")]
    public string cnic { get; set; }
}

[HttpPost]
    public JsonResult doesCnicExist(string employeeID, string cnic)
    {
        var empList = hc.employee.ToList();
        bool flag = false;
        foreach (employee e in empList)
        {
            if ((employeeID == e.employeeID) && (cnic == e.cnic))
            {
                flag = true;
            }
        }
        return Json(flag == false);
    }

On Create() action, it works great. But on Edit() action, program sees cnic already exist. And I cannot update employee with the same cnic. I cannot figure out how I can use additional employeeID field to achieve uniquness of employee object while editing?

What is the difference between int id and string employeeID? And you need to show the doesCnicExist() method you have tried. — user3559349
– user3559349, Commented Mar 21, 2016 at 2:06
@StephenMuecke int id is autogenrated by the database for the table and Employee ID is assigned by the organization. I am sorry I have been totally unable to think about a possible logic for this situation - for doesCnicExist(). That's why I asked this question. — Jogi
– Jogi, Commented Mar 21, 2016 at 2:11
But you said it works for your Create() action. So show it and then it can be corrected to work for the Edit() method. (Bu as far as the id and employeeID fields go, what is the point of having 2 identifier fields? - you should be using the id field in AdditionalFields since that's the key) — user3559349
– user3559349, Commented Mar 21, 2016 at 2:14
@StephenMuecke I got your point. But what difference it makes, since id will also always exist while editing. I have uploaded doesCnicExist. — Jogi
– Jogi, Commented Mar 21, 2016 at 2:16

Community · Accepted Answer · 2017-05-23 11:59:32Z

6

Since id is your unique identifier, you need to pass that to the doesCnicExist() method and then you can modify the logic to ignore exiting rows where the id already exists. Change the model to

public class employee
{
    [Key]
    public int id { get; set; }
    ....
    [Required]
    [Remote("doesCnicExist", "employee", AdditionalFields = "id", HttpMethod = "POST", ErrorMessage = "A user with this cnic already exists. Please enter a different cnic.")]
    public string cnic { get; set; }
}

and the controller method to

[HttpPost]
public JsonResult doesCnicExist(string cnic, int id)
{
    return Json(IsUnique(cnic, id));
}

private bool IsUnique(string cnic, int id)
{
  if (id == 0) // its a new object
  {
    return !hc.employee.Any(x => x.cnic == cnic);
  }
  else // its an existing object so exclude existing objects with the id
  {
    return !hc.employee.Any(x => x.cnic == cnic && x.id != id);
  }
}

Note that I have separated the logic into a separate method because RemoteAttribute is client side validation only and validation should always be performed on the server (client side validation should be considered a nice bonus, but a malicious user can easily bypass it). The separate method also allows you to validate it in the Create() and Edit() POST methods to prevent a possible exception being thrown when you save to the database.

But because RemoteAttribute is a client side (UI) attribute, it should not be applied to a data model anyway, and you should be following best practice and using a view model where the attribute is applied to your view model property and not the data model. I also recommend you use normal naming conventions for your classes and property names (i.e. PascalCase).

edited May 23, 2017 at 11:59

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answered Mar 21, 2016 at 2:36

user3559349

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7 Comments

user3559349 Over a year ago

Side note: Refer this DotNetFiddle for an example of how it works

Jogi Over a year ago

After your suggested solution, I am sorry but [HttpPost] Create() is not firing. When I press Create button, program just jams there.

user3559349 Over a year ago

What do you mean - nothing in my code has anything to do with your Create() method - you have not even shown it in your question

user3559349 Over a year ago

The only thing I can think of is that you have not included a hidden input for the id property in your create view so therefore the value of id is null which would result in an exception. If that is the case, make the parameter nullable - doesCnicExist(string cnic, int? id)

user3559349 Over a year ago

And ditto for IsUnique(string cnic, int? id). Then change the code in the IsUnique() method to if (!d.HasValue) and return !hc.employee.Any(x => x.cnic == cnic && x.id != id.Value);

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