<riaControls:DomainDataSource x:Name="z_rb_struc_Edit" 
                                          QueryName="GetRb_struc_add"  
                                          Style="{StaticResource DomainEditStyle}" />
            <riaControls:DomainDataSource x:Name="z_institute_Edit" 
                                          QueryName="GetZ_institute_Edit"  
                                          Style="{StaticResource DomainEditStyle}" />

<toolkit:DataForm x:Name="DFEdit_Inst"
                          ItemsSource="{Binding ElementName=z_rb_struc_Edit, Path=Data}"
                          Style="{StaticResource DataFormStyle_inst}" >
            <toolkit:DataForm.NewItemTemplate>
                <DataTemplate>
                    <StackPanel>
                        <toolkit:DataField Label="Наименование" FontWeight="Bold">
                             <TextBox Text="{Binding Path=name, Mode=TwoWay}" FontWeight="Normal" />
                        </toolkit:DataField>
                            <toolkit:DataField Label="Примечание" FontWeight="Bold" 
//Поле "remark" принадлежит уже другой таблицы. С источником DomainDataSource  z_institute_Edit
                                <TextBox Text="{Binding Path=remark, Mode=TwoWay}" 
                                     TextWrapping="Wrap" FontWeight="Normal"
                                     Name="Boxremark" Height="50" 
                                     VerticalScrollBarVisibility="Visible"/>
                            </toolkit:DataField>
                        </StackPanel>
                </DataTemplate>
            </toolkit:DataForm.NewItemTemplate>
        </toolkit:DataForm>

 // Выполняется, когда пользователь переходит на эту страницу.
        protected override void OnNavigatedTo(NavigationEventArgs e)
        {
             DFEdit_Inst.ItemsSource = "{Binding ElementName=z_institute_Edit, Path=Data}";
            this.z_rb_struc_Edit.LoadDDSByNavigationContext(this.NavigationContext);
        }

<toolkit:DataField Label="Name:">
         <TextBox Text="{Binding Path=City.Name, Mode=TwoWay}"/>
</toolkit:DataField>

     public IQueryable<Customer> GetCustomer()
        {
            return this.ObjectContext.Customer.Include("City");
        }

            // Metadata classes are not meant to be instantiated.
private CustomerMetadata()
       {
       }
       [Include]
       public City City { get; set; }