How to catch Non-integer values mapped to integer properties in UpdateModel()

Question

Let's say you have an object called Person that looks like this:

class Person
{
  public int ID { get; set; }
  public string Name { get; set; }
  public int NumberOfCatsNamedEnder { get; set; }
}

I have a simple HTML form that exposes the properties that gets posted to an ASP.NET MVC action inside of my PersonController class. The issue I have is that if someone puts in the letter 'A' for NumberOfCatsNamedEnder, I get a The model of type 'Person' was not successfully updated. error. Since this happens while trying to update the Model, I can't find any way to check to see if someone passed in a non-integer value without resorting to

if(!IsInteger(formCollection["NumberOfCatsNamedEnder"]))
{
  ModelState.AddModelError(
    "NumberOfCatsNamedEnder",
    "Ender count should be a number");
}

Is there a better way to do this? I was able to find some information on custom ModelBinders; is that what is needed?

Answer 1

I really like the approach of using a presentation model. I'd create a class like this:

class PersonPresentation
{
    public int ID { get; set; }
    public string Name { get; set; }
    public string NumberOfCatsNamedEnder { get; set; }

    public void FromPerson(Person person){ /*Load data from person*/ }
}

Then your controller action can bind the view to a PersonPresentation:

public ActionResult Index()
{
    Person person = GetPerson();
    PersonPresentation presentation = new PersonPresentation();
    ViewData.Model = presentation.FromPerson(person);
    return View();
}

...and then accept one in your Update method and perform validation:

public ActionResult Update(PersonPresentation presentation)
{
    if(!IsInteger(presentation.NumberOfCatsNamedEnder))
    {
        ModelState.AddModelError(
          "NumberOfCatsNamedEnder",
          "Ender count should be a number");
    }
    ...
}