Exclude properties on model binding using interfaces

Question

This is an example I have lifted here: http://aspalliance.com/1776_ASPNET_MVC_Beta_Released.5

public ActionResult Save(int id)
{
 Person person = GetPersonFromDatabase(id);
 try
 {
  UpdateMode<IPersonFormBindable>(person)
  SavePersonToDatabase(person);

  return RedirectToAction("Browse");
 }
 catch
 {
  return View(person)
 }
}

interface IPersonFormBindable
{
 string Name  {get; set;}
 int Age   {get; set;}
 string Email {get; set;}
}

public class Person : IBindable
{
 public string Name   {get; set;}
 public int Age    {get; set;}
 public string Email {get; set;}
 public Decimal? Salary  {get; set;}
}

This will not map values to property Salary but will execute its validation attributes which is not expected when you do the standard [Bind(Exclude="Salary")]

[Bind(Exclude="Salary")]
public class Person
{
 public string Name  {get; set;}
 public int Age   {get; set;}
 public stiring Email {get; set;}
 public Decimal? Salary  {get; set;}
}

How will I implement the [Bind(Exclude="Property")] using this interface pattern?

Darin Dimitrov · Accepted Answer · 2010-12-18T16:40:34.653

Here's what I would recommend you: use view models, and drop those interfaces, don't clutter your controllers with so much code. So you don't need the salary to be bound in this specific action: great, use a specifically tailored view model to this view:

public class PersonViewModel
{
    public string Id { get; set; }
    public string Name { get; set; }
    public int Age { get; set; }
    public string Email { get; set; }
}

And your controller action:

public ActionResult Save(PersonViewModel person)
{
    _repository.SavePersonToDatabase(person);
    return RedirectToAction("Browse");

    // Notice how I've explicitly dropped the try/catch,
    // you weren't doing anything meaningful with the exception anyways.
    // I would simply leave the exception propagate. If there's 
    // a problem with the database it would be better to redirect 
    // the user to a 500.htm page telling him that something went wrong.
}

If in another action you needed the salary then write another view model specific to this view. Don't worry if you repeat some of the properties between your view models. That's exactly what they are meant for. Obviously your repository will work with a model and not view model. So you will need to map between those two types. I would recommend you using AutoMapper for this purpose.

That's my point of view: always write view models specifically tailored to the needs of a given view. Try to avoid those Include, Exclude or one day it will bite you, someone is going to add some sensitive property and will forget to add it to the Exclude list. And even if you used Include it is still ugly.

where do you place validation? on the viewmodel or on the domain model? — Aivan Monceller, Dec 19 '10 at 22:26
@geocine, on the view model, this is what the controller receives from a view, this is what represents the user input, this is where the first level of validation should be performed. Simple validation like required properties, datetime formats, ... Business validation like whether an user already exists in the datastore should be performed at the service level which is a second level of validation. This is where the business rules are validated. — Darin Dimitrov, Dec 19 '10 at 22:30

Exclude properties on model binding using interfaces

1 Answers1