confused with html helper in ASP.NET

Question

I have a view model class

public class NewCustomerViewModel
{
   public IEnumerable<MembershipType> MembershipType { get; set; }
   public Customer Customer { get; set; }
}

and I have a Customers controller with New() action method :

public ActionResult New()
{
    var membershipTypes = _context.MembershipTypes.ToList();
    var viewModel = new NewCustomerViewModel
    {
        MembershipType = membershipTypes
    };

    return View(viewModel);
}

the view is :

@using (Html.BeginForm("Create", "Customers"))
{ 
    <div class="form-group">
        @Html.LabelFor(e => e.Customer.Name)
        @Html.TextBoxFor(e => e.Customer.Name, new { @class = "form-control" })
    </div>
    <div class="form-group">
        @Html.LabelFor(e => e.Customer.Birthdate)
        @Html.TextBoxFor(e => e.Customer.Birthdate, new { @class = "form-control" })
    </div>
    <div class="checkbox">
        <label>
           @Html.CheckBoxFor(e => e.Customer.IsSubscribedToNewsletter, new { @class = "checkbox" }) Subscribed To Newsletter?
        </label>
    </div>

For example, what's this for?

@Html.TextBoxFor(e => e.Customer.Name, ...)

we just have an empty Customer instance at the moment and we are trying to get the name?

Im not fully understanding your question, can you please try and refine what youre saying and be explicit with a question. Also, let us know what you're expecting to happen — Simon Price, Jan 30 '17 at 11:58
You may need to create a new Customer object in you model, At present it is null. — apc, Jan 30 '17 at 12:00
*"I am not quite confused with html helper"* ... well, that's good, right? — Manfred Radlwimmer, Jan 30 '17 at 12:08

score 0 · Accepted Answer · edited May 23 '17 at 12:01

0

I had this same question a while ago.

Though you are never instantiating Customer, the object is defined and the engine is able to build your view for it.

On postback, the ModelBinder will instantiate a new Customer and try to populate it back up from your form values. The web is stateless, so it doesn't matter if you sent in a pre-populated Customer object or an empty one when building the form, on postback ASP.NET can only construct it from what's in the form.

edited May 23 '17 at 12:01

Community

1
1

answered Jan 30 '17 at 12:03

Jonesopolis

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So there are two Customer objects? One empty, one with form values as properties? It is just weird to me for just have a null Customer object doing nothing? – Jan 30 '17 at 12:46
1

on the `GET` request, there's an object that contains a null `Customer` object, but still has metadata about the `Customer`. On postback, the ModelBinder will instantiate the `Customer` object and attempt to fill it in for your controller. – Jonesopolis Jan 30 '17 at 13:00
The html helper (`@Html.TextBoxFor(e => e.Customer.Name, ...`) is getting the metadata about the `Customer.Name` object to create labels for that input – Jonesopolis Jan 30 '17 at 13:01

confused with html helper in ASP.NET

1 Answers1