DropDownList用于绑定到模型

Question

I am new to asp.net mvc and despite several searches can't get my head successfully around drop down lists in a view.

Specifically I'm creating a project that is entity framework code first.

I have a form that requires the user to optionally pick the Licence Type they have.

And help or assistance would be greatly appreciated. I'm looking to create a DropDownListFor helper in the view to enable the drop down list for LicenceType.

The GRCMember model section relating to licence type is:

public class GRCMember
{
    [Column(TypeName = "int")]
    public int? LicenceTypeId { get; set; }
}

The Licence Type Model is:

public class LicenceType
{
    public int LicenceTypeId { get; set; }
    [StringLength(150)]
    [Column(TypeName = "nvarchar")]
    public String Type { get; set; }
    [Column(TypeName = "bit")]
    public bool? Dormant { get; set; }
    public virtual ICollection<GRCMember> GRCMembers { get; set; }
}

The associated Register View Model section is:

public class RegisterViewModel
{
    [Display(Name = "Licence Type")]
    public int? SelectedLicenceTypeId { get; set; }
}

The get controller method is:

[AllowAnonymous]
[HttpGet]
public ActionResult Register()
{
    return View();
}

And finally the drop down section of the view is:

@model GRCWebApp.Models.RegisterViewModel
<div class="col-md-3 col-md-offset-1">
    @Html.LabelFor(model => model.SelectedLicenceTypeId, htmlAttributes: new { @class = "control-label" })
    @Html.EditorFor(model => model.SelectedLicenceTypeId, new { htmlAttributes = new { @class = "form-control" } })
    @Html.ValidationMessageFor(model => model.SelectedLicenceTypeId, "", new { @class = "text-danger" })
</div>

Answer 1

Let's assume that you have two entities called Person and City. Then you would use a ViewModel in order to populate these two entities in a model as shown below:

PersonViewModel:

public Person Person { get; set; }
public IEnumerable<City> Cities { get; set; }

The controller of course returns the ViewModel:

Controller:

public ViewResult Create()
{
    PersonViewModel model = new PersonViewModel
    {
        Person = new Person (),
        Cities = repository.Cities.ToList()
    };
    return View(model);
}

You should pass the ViewModel to your View and then use the Dropdownlist as shown below:

View:

@model Project.WebUI.Models.PersonViewModel
...
@Html.LabelFor(m => m.Person.City)
@Html.DropDownListFor(m => m.Person.City, new SelectList(Model.Cities, "CityID", "CityName"), "---- Select ----")

Hope this helps...