.net mvc dropdownlist selected value not being updated - entity-framework

Question

I have two models defined as follows:
public class Division
{
public int DivisionID { get; set; }
[Required]
public string DivisionName { get; set; }
public virtual Employee Contact{ set;get; }
public virtual ICollection<Employee> Employees { get; set; }
}
public class Employee
{
public int EmployeeID{ get; set; }
public string Name{ get; set; }
public virtual Division Division{set;get;}
}
Entity framework sets a field in division table called employee_employeeid, how can I create dropdown for employees for the contact attribute in the division table.
Here is what I have tried but nothing is being sent to the database.
ViewBag.contact = new SelectList(db.Employees,"EmployeeID","Name");
In the view I have:
#Html.DropDownList("contact",String.Empty)
Is there a naming convention I have to use?
Edit
POST action:
[HttpPost]
public ActionResult Edit(Division division)
{
if (ModelState.IsValid)
{
db.Entry(division).State = EntityState.Modified;
db.SaveChanges();
return RedirectToAction("Index");
}
ViewBag.employeeid = new SelectList(
db.Employees, "EmployeeID", "EmployeeFirstName", division.employee);
return View(division);
}

Answer 1

I would recommend actually using ViewData instead of the ViewBag. In your controller have the following:
var employees = db.Employees.Select(e => new DropDownItem{ Text = e.Name, Value = e.EmployeeID });
ViewData["Employees"] = employees;
Then, in your view, have the following to display it:
#Html.DropDownList("Contact", ((IEnumerable<DropDownItem>)(ViewData["Employees"])))

Answer 2

I would suggest that you expose a foreign key property in your model. It makes the binding to the dropdown list and the later update much easier. Your Division model would look like this:
public class Division
{
public int DivisionID { get; set; }
[Required]
public string DivisionName { get; set; }
[ForeignKey("Contact")]
public int ContactId { set;get; }
public virtual Employee Contact { set;get; }
public virtual ICollection<Employee> Employees { get; set; }
}
Then in the Edit GET action you fill the ViewBag as you did:
ViewBag.Contacts = new SelectList(
db.Employees, "EmployeeID", "Name", division.ContactId);
You have a strongly typed view with the Division as model:
#model MyNamespace.Division
In this view you can bind the dropdown list to the ContactId property:
#Html.DropDownListFor(model => model.ContactId, ViewBag.Contacts)
Your POST action can be similar to your current version:
[HttpPost]
public ActionResult Edit(Division division)
{
if (ModelState.IsValid)
{
db.Entry(division).State = EntityState.Modified;
db.SaveChanges();
return RedirectToAction("Index");
}
ViewBag.Contacts = new SelectList(
db.Employees, "EmployeeID", "Name", division.ContactId);
return View(division);
}
Note, that it is in many cases the better practice (especially for security reasons) to use a special ViewModel instead of a database entity for your views. You could then incorporate the Contacts collection into your ViewModel (instead of using the ViewBag). To update the entity in the database you would load it and write the changed properties from the ViewModel to the entity and then save it.