Question

I have a details page which lets me edit the information associated with a particular item.

    public ActionResult Details(int id)
    {
        Call call = db.Calls.Find(id);
        return View(new CallFormViewModel(call));
    }

I use a view model —

public class CallFormViewModel
{
    public Call     Call    { get; private set; }

    public CallFormViewModel()
    {
        Call = new Call();
    }

    public CallFormViewModel(Call call)
    {
        Call = call;
    }
 }

When I submit, I want to only allow certain properties of the ‘call’ object to be updated. My Post handling method looks like this –

    [HttpPost]
    public ActionResult Details(CallFormViewModel callForm)
    {

         (some code removed for clarity)

         UpdateModel(callForm.Call ,new string[] {
            "Contact",
            "Summary",
            "Description",
        }

    }

The problem is that callForm has already been updated with all of the input from the form submit before I even call UpdateModel.

How can I change this and use UpdateModel to selectively update fields?

Thanks

Edit:

I think i’ve been looking at this the wrong way. What I should be doing is this:

    [HttpPost]
    public ActionResult Details(int id, CallFormViewModel callForm)
    {

         var call = db.Calls.Find(id);

         (some code removed for clarity)

         UpdateModel(call, "Call", new string[] {
            "Contact",
            "Summary",
            "Description",
        }

    }

This way it’s taking the incomplete data [and only the fields i want] and applying it to the actual model. I had been confusing the callForm.Call with the actual model object, when infact it’s only a representation of it.

Have to wait till I get to work to test this theory.

Answer 1

When you write your ViewModel in the Action parameters, The Model Binder Bind the ViewModel properties to the “incoming” data. This should work:

[HttpPost]
public ActionResult Details()
{
    CallFormViewModel callForm = new CallFormViewModel();

     UpdateModel(callForm.Call ,new string[] {
        "Contact",
        "Summary",
        "Description",
    }
}

---

Update:

The Bind attribute option:

[Bind(Include = "Contact,Summary,Description")]
public class CallFormViewModel
{
    // As before...
}