How do you post data to joined tables - Using EF 5, ASP.NET MVC 4 - asp.net-mvc

Question

I am new to MVC 4 and up to this point I have been retrieving data from one table and saving back to the same table. Now I have data from joined tables and need to save back to the same joined tables. I created a new model and created the get controller but when I try to save I get an error. Any constructive help would be appreciated.
Model
public partial class JoinClass
{
public string Name { get; set; }
public int EEID { get; set; }
public string Category { get; set; }
public int Points { get; set; }
public string Programs { get; set; }
public DateTime EntryDate { get; set; }
public DateTime Quarter { get; set; }
}
Controller
public ActionResult Create()
{
ViewBag.VBQuarter = new SelectList(db.Quarter2, "Id_Quarter2", "Quarter");
ViewBag.VBEEID = new SelectList(db.Users2, "Id_Users2", "EEID");
ViewBag.FK_Programs = new SelectList(db.Programs, "Id_Programs", "Programs");
ViewBag.EntryDate = DateTime.Now;
return View();
}
//
// POST:
[HttpPost]
public ActionResult Create(JoinClass joinclass)
{
if (ModelState.IsValid)
{
db.JoinClass.Add(joinclass);
db.SaveChanges();
return RedirectToAction("Index");
}
return View(joinclass);
}
View
#model 2014_V4.Models.JoinClass
#{
ViewBag.Title = "Create";
}
<h2>Create</h2>
#using (Html.BeginForm()) {
<fieldset>
<legend>Points</legend>
<div class="editor-label">
Quarter
</div>
<div class="editor-field">
#Html.DropDownList("VBQuarter")
</div>
<div class="editor-label">
User
</div>
<div class="editor-field">
#Html.DropDownList("VBEEID")
</div>
<div class="editor-label">
Programs
</div>
<div class="editor-field">
#Html.DropDownList("FK_Programs", String.Empty)
</div>
<div class="editor-label">
Points
</div>
<div class="editor-field">
#Html.EditorFor(model => model.Points)
</div>
<div class="editor-label">
Entery Date
</div>
<div class="editor-field">
#Html.TextBoxFor(model => model.EntryDate, new {#Value = ViewBag.EntryDate, #readonly="readonly" })
</div>
<p>
<input type="submit" value="Create" />
</p>
</fieldset>
}
#section Scripts {
#Scripts.Render("~/bundles/jqueryval")
}

Answer 1

Your problem is in constructor of JoinClass. You should not initialize virtual navigation properties collection with new HashSet<T>. Entity framework use its own collection type - EntityCollection<T>. You should not initialize navigation property collections at all.
PS: It is good practice to use special viewmodels with views and pass data from viewmodels to entity models explicit.