ASP.NET Core MVC validate list of objects read from file

Question

This is in ASP.NET Core MVC 2.1.

So what I want to do is validate a list of objects I read from a file.

The controller successfully reads the file and gets the data. I am using a DTO version of the model, heard it is better to do like that.

The main entity model.

public class Person
{
    [Key]
    public int ID { get; set; }

    [Required(ErrorMessage = "Osoba obavezno mora imati ime")]
    public string FirstName { get; set; }

    [Required(ErrorMessage = "Osoba obavezno mora imati prezime")]
    public string LastName { get; set; }

    [Required(ErrorMessage = "Grad obavezno mora imati ime")]
    public string CityName { get; set; }

    [Required(ErrorMessage = "Osoba obavezno mora imati postanski broj")]
    [StringLength(5, MinimumLength = 5, ErrorMessage = "Poštanski broja mora sadrži točno 5 znamenki.")]
    [RegularExpression("^[0-9]*$", ErrorMessage = "Poštanski broj smije sadržavati samo znamenke.")]
    public string PostalCode { get; set; }

    [Required(ErrorMessage = "Osoba obavezno mora imati mobilni broj")]
    [StringLength(11, MinimumLength = 11, ErrorMessage = "Mobilni broja mora sadrži točno 11 znamenki.")]
    [RegularExpression("^[0-9]*$", ErrorMessage = "Mobilni broj smije sadržavati samo znamenke.")]
    public string MobileNumber { get; set; }

    public string FullName => $"{FirstName} {LastName}";
}

The DTO entity model.

public class PersonModel
{
    public string FirstName { get; set; }
    public string LastName { get; set; }
    public string CityName { get; set; }
    public string PostalCode { get; set; }
    public string MobileNumber { get; set; }
}

The method used in the controller.

public IActionResult LoadData()
{
    PeopleService peopleService = new PeopleService();
    var path = "pathToFile";

    var resultData = peopleService.ReadCSVFile(path);
    return PartialView("_LoadDataTable", resultData);
}

So now my question is what is the best way to validate the data from the file?

I experimented using the entity model it worked, but I seems like a bad idea because you have to call the database every time. I want to validate it client side first I guess. Also, I need to get the error message back so that I can display it on view.

Answer 1

You can use TryValidateModel to valid the object from file. Document

You need to convert the string to a specific object fisrt, then call TryValidateModel.

public IActionResult LoadData()
    {
        
        //read the content from file and convert it to Person
        string readText = "";
        FileStream fileStream = new FileStream(@"path", FileMode.Open);
        using (StreamReader reader = new StreamReader(fileStream))
        {
            readText += reader.ReadToEnd();
        }
        var person = JsonConvert.DeserializeObject<Person>(readText);
        
        var valid=TryValidateModel(person);

        List<string> listError = new List<string>();
        foreach(var value in ModelState.Values)
        {
                if (value.Errors.Count > 0)
                    listError.Add(value.Errors[0].ErrorMessage);
        }
        
        ViewBag.errors = listError;
        //...
    }

View

@foreach(var e in (List<string>)ViewBag.errors)
{
<span class="text-danger">@e</span>
}

Another way is to use ValidationSummary in the view.

@Html.ValidationSummary()