MVC 5在主实体创建期间创建外键实体

Question

I am utterly new to MVC and asp.net with Entity Framework so I am sure that most of my trouble stems from not knowing the proper terminology for what I am trying to do.

I have an "Address" database table/ entity that is a street address. Rather than having the street address fields in every entity that has an associated address, I simply have a foreign key column that points to the correct address in the address table.

For my Location creation view model, I have the following

public class LocationCreationViewModel
{
    public address Address { get; set; }
    [Key]
    public location Location { get; set; }

}

It is probably worth pointing out that that View model is "hand made" while the address and location member objects are managed by the entity framework

My Create View has all of the location data, and then includes a partial address view which is rendered with Html.Partial("_AddressCreate", Model.Location)

What currently happens is the LocationCreationViewModel returned in the Create(model) function is LocationCreationViewModel is null, or each of the fields is null. In any event, none of the data from the view is populated in the view model.

What I want to happen is that I get back the 2 addresses, add them to the address table in the database, then add my order to the order database with FK address fields pointing to the 2 newly created addresses.

I am using MVC5 and EF6 in visual studio 2017

Create.cshtml

@model MyWeb.Models.LocationCreationViewModel

@{
    ViewBag.Title = "Create";
}

<h2>Create</h2>

@using (Html.BeginForm()) 
{
    @Html.AntiForgeryToken()

<div class="form-horizontal">
    <h4>location</h4>
    <hr />
    @Html.ValidationSummary(true, "", new { @class = "text-danger" })
    <div class="form-group">
        @Html.LabelFor(model => model.Location.name, htmlAttributes: new { @class = "control-label col-md-2" })
        <div class="col-md-10">
            @Html.EditorFor(model => model.Location.name, new { htmlAttributes = new { @class = "form-control" } })
            @Html.ValidationMessageFor(model => model.Location.name, "", new { @class = "text-danger" })
        </div>
    </div>

    <div class="form-group">
        @Html.LabelFor(model => model.Location.address, "address", htmlAttributes: new { @class = "control-label col-md-2" })
        <div class="col-md-10">
            @Html.DropDownList("address", null, htmlAttributes: new { @class = "form-control" })
            @Html.ValidationMessageFor(model => model.Location.address, "", new { @class = "text-danger" })
        </div>
    </div>
    @Html.Partial("_AddressPartial", Model.Address)

    <div class="form-group">
        <div class="col-md-offset-2 col-md-10">
            <input type="submit" value="Create" class="btn btn-default" />
        </div>
    </div>
</div>
}

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

_AddressPartial.cshtml

@model MyWeb.Data.address

    <div class="form-horizontal">
        <h4>address</h4>
        <hr />
        @Html.ValidationSummary(true, "", new { @class = "text-danger" })
        <div class="form-group">
            @Html.LabelFor(model => model.country, htmlAttributes: new { @class = "control-label col-md-2" })
            <div class="col-md-10">
                @Html.EditorFor(model => model.country, new { htmlAttributes = new { @class = "form-control" } })
                @Html.ValidationMessageFor(model => model.country, "", new { @class = "text-danger" })
            </div>
        </div>


        <div class="form-group">
            @Html.LabelFor(model => model.locality, htmlAttributes: new { @class = "control-label col-md-2" })
            <div class="col-md-10">
                @Html.EditorFor(model => model.locality, new { htmlAttributes = new { @class = "form-control" } })
                @Html.ValidationMessageFor(model => model.locality, "", new { @class = "text-danger" })
            </div>
        </div>

        <div class="form-group">
            @Html.LabelFor(model => model.postalCode, htmlAttributes: new { @class = "control-label col-md-2" })
            <div class="col-md-10">
                @Html.EditorFor(model => model.postalCode, new { htmlAttributes = new { @class = "form-control" } })
                @Html.ValidationMessageFor(model => model.postalCode, "", new { @class = "text-danger" })
            </div>
        </div>


    </div>

LocationController::Create

[MyWebAuthorize(MyWebRole = MyWebRole.Admin)]
        public ActionResult Create()
        {
            ViewBag.address = new SelectList(db.addresses, "id", "country");
            ViewBag.id = new SelectList(db.inventories, "locationID", "locationID");

            LocationCreationViewModel model = new LocationCreationViewModel();
            return View(model);
        }


[HttpPost]
        [ValidateAntiForgeryToken]
        public async Task<ActionResult> Create( LocationCreationViewModel location)
        {
            if (ModelState.IsValid)
            {
                db.addresses.Add(location.Address); //null reference exception here
                db.locations.Add(location.Location);

                await db.SaveChangesAsync();
                return RedirectToAction("Index");
            }

            ViewBag.address = new SelectList(db.addresses, "id", "country", location.Location.address);
            ViewBag.id = new SelectList(db.inventories, "locationID", "locationID", location.Location.id);
            return View(location);
        }

Answer 1

The autobinder failed to bind form data because of the field name Location in the View Model. I assume that this is due to Location being part of the page route. IE for the LocationController, the route would be /Location/Create

In any event, renaming LocationCreationViewModel::Location to LocationCreationViewModel::Locus fixed everything.