Asp.net MVC 发布表单空值

Question

I am currently following Mosh's asp.net mvc course.

Recently I got to using form to post data, but I encountered a problem that I cannot solve.

So the form for adding a Customer uses NewCustomerViewModel that contains available MembershipTypes . Then, in the form I use a drop down list to select one and bind it with this Customer.

However, after the submit, the MembershipType in Customer is set to null although MembershipTypeID is bound properly.

I have no idea how to solve this problem. Any advice is appreciated. Thank you in advance.

The code:

Customer class:

public class Customer
{
    public int ID { get; set; }
    [Required]
    [StringLength(70)]
    public String Name { get; set; }
    public bool IsSubscribedToNewsletter { get; set; }
    public MembershipType MemebershipType { get; set; }
    public int MembershipTypeID { get; set; }
    public DateTime? Birthdate { get; set; }
}

Customer controller:

public class CustomerController : Controller
{
    private ApplicationDBContext context;

    public CustomerController(ApplicationDBContext ctxt)
    {
        this.context = ctxt;
    }

    public CustomerController()
    {
        this.context = new ApplicationDBContext();
    }

    protected override void Dispose(bool disposing)
    {
        context.Dispose();
    }
    // GET: Customer
    public ActionResult Index()
    {

        var model = context.Customers.Include(x => x.MemebershipType).ToList();
        return View(model);
    }

    public ActionResult Details(int id)
    {
        var ct = context.Customers.Include(c => c.MemebershipType).SingleOrDefault(c => c.ID == id);
        if (ct == null) return HttpNotFound();
        return View(ct);
    }

    public ActionResult New()
    {
        var membershiptypes = context.MembershipTypes.ToList();
        var viewmodel = new NewCustomerViewModel
        {
            MembershipTypes = membershiptypes
        };
        return View(viewmodel);
    }
    [HttpPost]
    public ActionResult Create(Customer customer)
    {
        context.Customers.Add(customer);
        context.SaveChanges();
        return RedirectToAction("Index", "Customer");
    }
}

NewCustomerViewModel

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

View for adding a new customer:

    @model Vidly.ViewModels.NewCustomerViewModel
@{
    ViewBag.Title = "New";
    Layout = "~/Views/Shared/_Layout.cshtml";
}

<h2>New Customer</h2>

@using (Html.BeginForm("Create", "Customer"))
{
    <div class="form-group">
        @Html.LabelFor(c => c.Customer.Name)
        @Html.TextBoxFor(c => c.Customer.Name, new { @class = "form-control" })
    </div>
    <div class="form-group">
        <label>Date of birth</label>
        @Html.TextBoxFor(c => c.Customer.Birthdate, new { @class = "form-control" })
    </div>
    <div class="checkbox">
        <label>
            @Html.CheckBoxFor(c => c.Customer.IsSubscribedToNewsletter) Subscribed to newsletter?
        </label>
    </div>
    <div class="form-group">
        <label>Membership type</label>
        @Html.DropDownListFor(c => c.Customer.MembershipTypeID,
       new SelectList(Model.MembershipTypes, "ID", "Name"), "Select membership type", new {@class="form-control"})
    </div>

    <button type="submit" class="btn btn-primary">
        Save
    </button>
}  

Answer 1

This is normal since you did not set the MembershipType , you set the MembershipTypeId

and when it is saved in the database the MembershipTypeId is Saved

Then when you query this customer via the Details Action you will get the MembershipType populated properly.

Alternatively you can Populate it using the contextManager

By simply

customer.MembershipType = context.MembershipTypes.SingleOrDefault(m => m.id == customer.MembershipTypeId);

but this will cost you unnecessary round to the database.