EF 5.0 Foreign Key Not Updating - ef-code-first

Question

I know there are some other questions regarding this-- but I was unable to get them to solve my problem.
I have the following classes:
public class Category
{
public Category()
{
Products = new List<Product>();
}
public int Id { get; set; }
public string Name { get; set; }
public List<Product> Products { get; set; }
public override string ToString()
{
return String.Format("{0}{1}", Id, Name);
}
}
and
public class Product
{
public int Id { get; set; }
public string Name { get; set; }
public decimal Price { get; set; }
public Category Category { get; set; }
public override string ToString()
{
return String.Format("{0}{1}", Id, Name);
}
}
I've got some code which attempts to update both a product and it's category:
using (var ctx = GetCtx())
{
var beverages = new Category {Id = 1 };
var milk = new Product { Name = "MILK", Id = 4, Category = new Category { Id = 1} };
ctx.Entry(milk).State = System.Data.EntityState.Modified;
ctx.SaveChanges();
}
this results in the following sql statement:
update [dbo].[Products]
set [Name] = #0, [Price] = #1
where ([Id] = #2)
#0: MILK
#1: 0
#2: 4
I can't figure out how to make sure that the Category for the particular product is updated. I thought about adding a property to Product for Category_Id but this results in an additional column being generated in my database.
EDIT:
I think I figured this out-- after watching Julia Lerman's series on EF (Pluralsight)-- the way to set up this class is like this:
public class Product
{
public int Id { get; set; }
[Required]
[MaxLength(200)]
public string Name { get; set; }
public virtual Category Category { get; set; }
public int CategoryId { get; set; }
}
This results in only one foreign key column in the Products table. The Category of the Product gets updated when updating the CategoryId property.

Answer 1

You have to do two jobs, so do them in two operations...
var cat = ctx.Categories.FirstOrDefault(c=>c.Id == 1);
if(cat == null){
cat = new Category{Id=1};
ctx.Categies.Add(cat);
}
cat.Products.Add(new Product{Name="Milk", Id=4};
try{
ctx.SaveChanges();
}catch(Exception ex){
return RedirectToResponse("someone else got in first with that category Id");
}