Duplicate Record in one to one relationship when savechange - entity-framework

Question

i have a one to one relationship between two entity and whn i want set navigation property add duplication record tu my table
because my English is poor, i attach my Project for you Here
tnx
my code here:
here my Entity:
public partial class User
{
public int Id { get; set; }
public string Name { get; set; }
public string Lastname { get; set; }
public int UserType { get; set; }
}
public partial class Storage : User
{
public virtual Store Store { get; set; }
}
public partial class Store
{
public int Id { get; set; }
public string Name { get; set; }
public virtual Storage Storage { get; set; }
}
here my Add Store botton:
User u = (User)(comboBox1.SelectedItem);
Storage st = new Storage(u);
Store s = new Store(textBoxStorename.Text);
s.SetStorage(st);
s.Save(st);
and here my Store Class:
public partial class Store
{
public Store()
{
}
public Store(string name)
{
this.Name = name;
}
public void SetStorage(Storage s)
{
if (s != null)
{
this.Storage = s;
}
}
public void Save(Storage s)
{
using (var storekeeper = new TestContainer())
{
bool flag = false;
foreach (var item in storekeeper.Stores)
{
if (item.Equals(this))
{
flag = true;
}
}
if (flag)
{
MessageBox.Show("Duplicat Error", "", MessageBoxButtons.OK, MessageBoxIcon.Error);
return;
}
try
{
storekeeper.Users.Attach(s);
storekeeper.Stores.Add(this);
storekeeper.SaveChanges();
}
catch (Exception e )
{
MessageBox.Show(e.Message);
}
}
}
public override string ToString()
{
return this.Name;
}
}

Answer 1

The real problem here is your data model.
In any case, what's happening is you're recreating the User entity that already exists when you instantiate the new Storage instance. Storage inherits from User, so storage is an instance of user conceptually. The storage model, however, is different - Storage is a relationship table between User and Store.
By instantiating a new instance of Storage, copying the existing User object's properties to the base properties of the Storage instance, then simply attaching the Storage object to the Users DbSet, entity framework rightly thinks that the object is new and needs to be inserted - including the User entity object. The user record already exists, hence your duplicate key problem.
Solution: change your data model. No reason to have the 1..1 relationship entity "Storage". Simply create a nullable Store property in the User entity. If you want to enforce that an instance of Store can only be referenced by a single User, then the Store entity should either use the User.Id property as its primary key (with the FK relationship) or have a FK UserId property in Store that must be unique.