MVC 4 Conditional Model Validation with Entity Framework

Question

Is it possible to place conditions on a ViewModel where data equals a specific value in one field within the entity framework, the required element or entire object is removed from the ViewModel before using TryValidateModel on the ViewModel?

I would like to remove HomeValue and PurchasePrice from the Model validation where OwnOrRent (model.OwnOrRent) is not equal to 1 or 9.

Model.cs

public class Address
{
    public int Id { get; set; }

    [DisplayName("House Name or Number")]
    [StringLength(50)]
    public string HouseNameOrNumber { get; set; }

    [DisplayName("Post Town")]
    [StringLength(50)]
    public string PostTown { get; set; }

    [Required(ErrorMessage = "Own or Rent is Required")]
    [DisplayName("Own or Rent")]
    [StringLength(50)]
    public string OwnOrRent { get; set; }

    [Required(ErrorMessage = "Mortgage/Rent Amount is Required")]
    [DisplayName("Mortgage/Rent Amount")]
    [StringLength(50)]
    public string MortgageRent { get; set; }

    [Required(ErrorMessage = "Home Value is Required")]
    [DisplayName("Home Value")]
    [StringLength(50)]
    public string HomeValue { get; set; }

    [Required(ErrorMessage = "Purchase Price is Required")]
    [DisplayName("Purchase Price")]
    [StringLength(50)]
    public string PurchasePrice { get; set; }
}

HomeController.cs

public ActionResult Application(int id)
{
    var viewAddressModel = new Address();

    using (
        var dbEntities = new DbEntities(new EntityConnection(_df.DbEntities)))
    {
        var model = dbEntities.Applications.Single(e => e.Id == id);

        viewAddressModel.Id = Id;
        viewAddressModel.HouseNameOrNumber = model.HouseNameOrNumber;
        viewAddressModel.PostTown = model.PostTown;
        viewAddressModel.OwnOrRent = GetStatus(model.OwnOrRent);
        viewAddressModel.MortgageRent = model.MortgageRent.ToString();
        viewAddressModel.HomeValue = model.HomeValue;
        viewAddressModel.PurchasePrice = model.PurchasePrice;

        if (model.OwnOrRent != "1" || model.OwnOrRent != "9")
        {
            ModelState.Remove("HomeValue");
            ModelState.Remove("PurchasePrice");
        }

        if (!TryValidateModel(viewAddressModel))
        {
            return PartialView("Address", viewAddressModel);
        }
    }

    var vm = new ApplicationViewModel { Item = CreateApp(id) };

    return PartialView("Application", vm);
}

As you can see I have tried to use ModelState.Remove but this has no effect.

Any assistance with this would be much appreciated?

Answer 1

Based on your comments you want to populate a model from the database, then validate it (because its old data which may not be valid), but not display errors for HomeValue or PurchasePrice based on the value of OwnOrRent, in which case you need to call TryValidateModel first, then remove ModelState errors

var viewAddressModel = new Address();
.... // set values
if (!TryValidateModel(viewAddressModel))
{
  if (model.OwnOrRent != "1" || model.OwnOrRent != "9")
  {
    if (ModelState.ContainsKey("HomeValue"))
    {
      ModelState["HomeValue"].Errors.Clear();
    }
    if (ModelState.ContainsKey("PurchasePrice"))
    {
      ModelState["PurchasePrice"].Errors.Clear();
    }
  }
}

You can now use if (ModelState.IsValid) to check if there are any other validation errors and return the appropriate view

Side note: I just used your if condition relating to the OwnOrRent value, but I suspect what you really want is

if (!(model.OwnOrRent == "1" || model.OwnOrRent == "9"))

Answer 2

There is a thread about the different options to do conditional validation: ASP.NET MVC Conditional validation