Question

I have a domain model and a view model as follows:

Domain Model:

namespace MvcApplication1.Models
{
    public enum Sex { Male, Female };
    public class Person
    {
        public int Id { get; set; }
        public string Name { get; set; }

        [Required(ErrorMessage="Please select either Female or Male.")]
        public Sex? Sex { get; set; }
    }
}

View Model:

namespace MvcApplication1.ViewModels
{
    public class HomeCreateVM
    {
        public HomeCreateVM()
        {
        }
        public HomeCreateVM(Person p)
        {
            Person = p;
            SelectList = p.Sex.GetSelectList();
        }
        public Person Person { get; set; }
        public SelectList SelectList { get; set; }

    }
}

The auxiliary extension method is defined as follows:

namespace MvcApplication1.Models
{
    public static class Utilities
    {
        public static SelectList GetSelectList<XXX>(this XXX? obj) where XXX : struct
        {
            var values = from XXX x in Enum.GetValues(typeof(XXX))
                         select new { Text = x.ToString(), Value = x };
            return new SelectList(values, "Value", "Text", obj);
        }
    }
}

Controller:

public ActionResult Create()
{
    var p = new Person();

    return View(new HomeCreateVM(p));
}

[HttpPost]
public ActionResult Create(Person hc)// the source of problem!
{
    if (ModelState.IsValid)//always false!
    {
        TempData["status"] = hc;
        return RedirectToAction("Confirm");
    }
    else
        return View(new HomeCreateVM(hc));
}

HomeCreateVM.cshtml:

@model MvcApplication1.ViewModels.HomeCreateVM
<div>
    Name: @Html.EditorFor(model => model.Person.Name)</div>
<div>
    Sex: @Html.DropDownListFor(model => model.Person.Sex, Model.SelectList, "--Select--")</div>

Create View:

@model MvcApplication1.ViewModels.HomeCreateVM

@{
    ViewBag.Title = "Create";
}

<h2>Create</h2>

<script src="@Url.Content("~/Scripts/jquery.validate.min.js")" type="text/javascript"></script>
<script src="@Url.Content("~/Scripts/jquery.validate.unobtrusive.min.js")" type="text/javascript"></script>

@using (Html.BeginForm()) {
    @Html.ValidationSummary(true)
    <fieldset>
        <legend>HomeCreateVM</legend>
        @Html.EditorForModel()
        <p>
            <input type="submit" value="Create" />
        </p>
    </fieldset>
}

<div>
    @Html.ActionLink("Back to List", "Index")
</div>

Question:

There is no problem if the POST Create action method accepts a HomeCreateVM object as the argument.
However, if I change the POST Create action method argument from HomeCreateVM to Person (as shown in the code above), ModelState.IsValid always returns false.

The question is: “Is it possible to pass a ViewModel object to a Create view but only accept a DomainModel object from a POST Create action method?”

Answer 1

Because your view is strongly typed to the view model your form fields will look like this:

<input type="text" name="Person.Name" />

and if you want to bind correctly you need to specify the prefix:

[HttpPost]
public ActionResult Create([Bind(Prefix = "Person")]Person hc)
{
    ...
}