How do you do lookup tables via code first - ef-code-first

Question

I've been searching this without any luck on how to resolve. I have a list of available departments that can be used within my stores. Since stores vary, some departments may not exist and I want to keep track of how much shelving space each department has for each store. What's the best way to create this?
Here's my model:
public class Store
{
[Key]
[DatabaseGenerated(DatabaseGeneratedOption.None)]
public int ID { get; set; } //StoreNumber
public virtual List<StoreDepartment> StoreDepartments { get; set; }
}
public class StoreDepartment
{
[Key]
public int ID { get; set; }
public int StoreID { get; set; }
public Department Department { get; set; }
public int ShelvingLinealFT { get; set; }
}
public class Department
{
[Key]
[DatabaseGenerated(DatabaseGeneratedOption.None)]
public int ID { get; set; } //DepartmentNumber
public string Name { get; set; }
public bool InActive { get; set; }
}
I've already populated my Department tables, but when I attempt to save a StoreDepartment object, I get an error stating that it can't insert a row since its trying to create a duplicate key. It's like it's trying to create a new record.
Any help would be appreciated.
Here's the code for my DbContext:
public class StoresRepository:DbContext
{
public DbSet<Store> Stores { get; set; }
public DbSet<StoreDepartment> StoreDepartments { get; set; }
public DbSet<Department> Departments { get; set; }
}
Here is my Save method:
/// <summary>
/// Saves a StoreDepartment Object to the store("dept.storeid")
/// Adds a new record if ID is 0
/// </summary>
/// <param name="dept"></param>
/// <returns></returns>
public bool Save(StoreDepartment dept)
{
bool retval = false;
try
{
using (var db = new StoresRepository())
{
if (dept.ID.Equals(0))
{
//Add Store Department
db.StoreDepartments.Add(dept);
}
else
{
//this is an update
StoreDepartment department = db.StoreDepartments.Where(p => p.ID.Equals(dept.ID)).FirstOrDefault();
department.Department = dept.Department;
department.ShelvingLinealFT = dept.ShelvingLinealFT;
}
int rowsupdated = db.SaveChanges();
retval = true;
}
}
catch (Exception ex)
{
Utils.Trace(string.Format("StoresContext.cs: StoreDepartments.Save(). ID:{1}. Exception: {0}", ex, dept.ID), Utils.ErrorTypes.Error);
}
return retval;
}

Answer 1

You probably change the state of the Department to added when you add the StoreDepartment object. Something like this:
using(var db = new MyContext())
{
var storeDepartment = new StoreDepartment();
storeDepartment.StoreId = storeId;
storeDeparemtent.Department = department;
db.StoreDepartments.Add(storeDepartment); // also marks Department as added
db.SaveChanges();
}
The solution is to move up the line where you add the object:
using(var db = new MyContext())
{
var storeDepartment = new StoreDepartment();
db.StoreDepartments.Add(storeDepartment);
storeDepartment.StoreId = storeId;
....
}
You can also add a DepartmentId to the StoreDepartment class and set its value, as you do with StoreId. Together with the Department property this is called a foreign key association.

Answer 2

I figured it out.
Here are the correct models:
public class StoreDepartment
{
[Key]
public int ID { get; set; }
public int DepartmentID { get; set; }
public virtual Department Department { get; set; }
public int ShelvingFootage { get; set; }
}
public class Department
{
[Key]
[DatabaseGenerated(DatabaseGeneratedOption.None)]
public int ID { get; set; }
public string Name { get; set; }
public bool Active { get; set; }
public virtual ICollection<StoreDepartment> StoreDepartments { get; set; }
}
Using Affluent API, I setup my relationships as follows:
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
modelBuilder.Entity<StoreDepartment>().HasRequired(d => d.Department);
modelBuilder.Entity<Department>().HasMany(d => d.StoreDepartments);
}
Once I had this setup, one of the main issues I had was with populating the object.
Normally, you would do the following:
StoreDepartment sd = new StoreDepartment();
sd.Department = new Department(){
ID = 302,
Name = "Deli"
};
sd.ShelvingFootage = 100;
However when trying to save this object, Entity would attempt to add a new record in the Department table which of course would throw an exception due to a violation in the primary key.
The trick was to not update this directly and to build my StoreDepartment object as follows:
StoreDepartment sd = new StoreDepartment();
sd.DepartmentID = 302;
sd.ShelvingFootage = 100;
By doing this, you are only updating the foreign key for the StoreDepartment.Department object.