EF CTP5 mapping fails on update

Question

I'm trying to make a one-to-many mapping, but I have some difficulties on saving updates.
Menu can have 0 to 1 module.
Module can have 0 to many menus.

When i make a new menu object and saves it, the module is saved into the db, but on update it isn't.

This is working:

var menu = new Menu()
menu.Title = "Menu Title";
menu.Module = repository.GetModule(2);

...
DbContext.SaveChanges()
...

Saves the menu item with the foreign key to the Module.
MenuID : 1
ModuleID : 2

When i'm trying to make an update like this:

var menu = repository.GetMenu(1);
menu.Module = repository.GetModule(3);

Edit: ... DbContext.SaveChanges() ...

The ModuleID in the Menu table isn't changed. What is wrong?

---

My model:

public class Menu
{
   [Key]
   public int MenuID { get; set; }
   public string Title { get; set; }
   public int ModuleID { get; set; } <-- Is this necessary

   public virtual Module Module { get; set; }
}

public class Module
{
   [Key]
   public int ModuleID { get; set; }
   public string Name { get; set; }

   public virtual ICollection<Menu> Menus { get; set; }
}

---

Mapping:

protected override void OnModelCreating(System.Data.Entity.ModelConfiguration.ModelBuilder modelBuilder)
{
   modelBuilder.Entity<Module>().HasMany<Menu>(m => m.Menus).WithOptional().HasForeignKey(m => m.ModuleID);
}

To get my mapping working I had to add the ModuleID to the Menu class, but can I map this different?

Edit:

I'm using MySQL

Menu table:
int MenuID
varchar Title
int ModuleID

Module table:
int ModuleID
varchar Name

Answer 1

Finally i figured it out. It was a stupid noob error:

public ActionResult Edit(int id, MenuModel menu)
{
   var menuDb = repository.Get(id);
   TryUpdateModel(menuDb);

   //repository.save(menu); <-- WRONG!
   repository.save(menuDb); <-- BINGO... It works! 
}