“无法定义两个对象之间的关系，因为它们被附加到不同的ObjectContext对象。” -错误

Question

First of all I would like to mention that I have scoured the internet to find the solution to the problem however I couldn't get anything to work. I'm fairly new to EF so I don't have a complete understanding of DBContext or ObjectContexts so further explanation may be required. My EF code was built database first.

My Scenario

I have two tables in my data model:

Below is my DriveDB class where I have my Client_Type attached (along with others that I have left out of the example for simplicity).

public partial class DriveDB : DbContext
{
    public DriveDB()
        : base("name=DriveDB")
    {
    }

    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        throw new UnintentionalCodeFirstException();
    }

    public virtual DbSet<Client_Type> Client_Type { get; set; }
    public virtual DbSet<Entity> Entities { get; set; }
    public virtual DbSet<EntityContact> EntityContacts { get; set; }
    public virtual DbSet<Person> People { get; set; }
}

---

public class DataAccessService : IDataAccessService
{
    DriveDB MainRepository;
    public DataAccessService()
    {
        MainRepository = new DriveDB();
    }
    public void CommitChanges()
    {
        MainRepository.SaveChanges();
    }
}

My logic is that since the Client_Type tables is now attached all I have to do to update those tables is run the .SaveChanges() method and both tables will be updated. This is not the case however as apparently they don't share the same ObjectContext . I realize there is a difference between DBContext and ObjectContext but I don't know how to overcome this problem.

I have attempted to detach and attach Client_Type to DriveDB however I never found the correct solution.

How can I update the database without the compiler throwing an exception?

Xaml:

<ComboBox Style="{StaticResource DataComboBox}" ItemsSource="{Binding Client_type_list}" SelectedItem="{Binding Record.Client_Type, Mode=TwoWay}" ItemTemplate="{StaticResource Client_typeDataTemplate}"/>

<DataTemplate x:Key="Client_typeDataTemplate">
            <TextBlock Text="{Binding client_type1}"/>
        </DataTemplate>

Answer 1

You have to update the state to every entry from every table as modified. The tables are related, but they are still separate tables in your DbContext. You can read more about your case here : http://www.asp.net/mvc/overview/older-versions/getting-started-with-ef-5-using-mvc-4/updating-related-data-with-the-entity-framework-in-an-asp-net-mvc-application

Answer 2

So for those of you that are interested here is the solution I found.

My ItemSource for the ComboBox was bound to this property:

public List<Client_Type> Client_type_list
{
   get { return ServerPxy.GetClientTypes(); }
}

This made the ComboBox not only fail to read the SelectedItem value from the Record property but also throw the above exception when I tried to update the database with the new value.

I now have a property that only obtains the value from he database when the UserControl is loaded:

private List<Client_Type> client_type_list;
public List<Client_Type> Client_type_list
{
    get { return client_type_list; }
    set
    {
        client_type_list = value;
        RaisePropertyChanged("Client_type_list");
    }
}

public void LoadExecute()
{
    Client_type_list = ServerPxy.GetClientTypes();
}

To reiterate... I believe the SelectedItem of the ComboBox must be set before the ItemSource