MVC3 - How to add dropdown to a form (Post) populated with different entity - asp.net-mvc

Question

Hi I am working in a MVC 3 application. I have a Create Form with following code.
#model Xrm.Student
#{
ViewBag.Title = "Create Student Record";
}
#using (Html.BeginForm("Create", "Student", FormMethod.Post))
{
<div class="editor-label">
#Html.LabelFor(model => #Model.FirstName)
</div>
<div class="editor-field">
#Html.EditorFor(model => #Model.FirstName)
#Html.ValidationMessageFor(model => #Model.FirstName)
</div>
<div>
<input id="Submit1" type="submit" value="Submit" />
</div>
}
I want to add a new drop down under Firsname field which should be populated with pubjects. Subject is different Entity. I could be very easy, but I am newbie with MVC so I just stuck here. Can anyone please suggest me the way to achieve it.
Thanks and Regards

Answer 1

I would define a view model:
public class MyViewModel
{
public Student Student { get; set; }
[DisplayName("Subject")]
[Required]
public string SubjectId { get; set; }
public IEnumerable<Subject> Subjects { get; set; }
}
and then have your controller populate and pass this view model to the view:
public ActionResult Create()
{
var model = new MyViewModel();
model.Student = new Student();
model.Subjects = db.Subjects;
return View(model);
}
and finally have your view strongly typed to the view model:
#model MyViewModel
#{
ViewBag.Title = "Create Student Record";
}
#using (Html.BeginForm())
{
<div class="editor-label">
#Html.LabelFor(x => x.Student.FirstName)
</div>
<div class="editor-field">
#Html.EditorFor(x => x.Student.FirstName)
#Html.ValidationMessageFor(x => x.Student.FirstName)
</div>
<div class="editor-label">
#Html.LabelFor(x => x.SubjectId)
</div>
<div class="editor-field">
#Html.DropDownListFor(
x => x.SubjectId,
new SelectList(Model.Subjects, "Id", "Name"),
"-- Subject --"
)
#Html.ValidationMessageFor(x => x.SubjectId)
</div>
<div>
<input type="submit" value="Submit" />
</div>
}
The "Id" and "Name" values I used for the SelectList must obviously be existing properties on your Subject class that you want to be used as respectively binding the id and the text of each option of the dropdown.