Buon Giorno Sto tentando di recuperare la Propieta NegozioId Che è Foreign Key della Tabella Busta per salvare i dati nella tabella busta. Ma Non ci riesco,logicamente i dati della combo sono reperiti dalla Collezione NegozioOser ma poi non so come fare a iniettarli in Busta.NegozioID.

Questo é il Model:
codice:
[Table("Negozio")]publicpartialclassNegozio
    {
        publicNegozio()
        {
            Bustas=newHashSet<Busta>();
        }

        [DatabaseGenerated(DatabaseGeneratedOption.None)]
        publicintNegozioID{get;set;}

        [Required]
        [StringLength(10)]
        publicstringRagioneSociale{get;set;}

        publicvirtualICollection<Busta>Bustas{get;set;}}
Questo è Il ModelView:
codice:
using GalaSoft.MvvmLight;using System.Collections.ObjectModel;
using Prova1.Model;
using GalaSoft.MvvmLight.CommandWpf;
using Prova1.Service;




namespace Prova1.ViewModel
{
    /// <summary>
    /// This class contains properties that the main View can data bind to.
    /// <para>
    /// Use the <strong>mvvminpc</strong> snippet to add bindable properties to this ViewModel.
    /// </para>
    /// <para>
    /// You can also use Blend to data bind with the tool's support.
    /// </para>
    /// <para>
    /// See http://www.galasoft.ch/mvvm
    /// </para>
    /// </summary>
    public class MainViewModel : ViewModelBase
    {
        /// <summary>
        /// Initializes a new instance of the MainViewModel class.
        /// </summary>
        /// 
         IDataAccessService _serviceProxy;


         ObservableCollection<Busta> _Bustas;


         public ObservableCollection<Busta> BustaOservable
         {
             get { return _Bustas; }
             set
             {
                 _Bustas = value;
                 RaisePropertyChanged("BustaOservable");
             }
         }


         ObservableCollection<Negozio> _Negozios;


         public ObservableCollection<Negozio> NegozioObser


         {
             get { return _Negozios; }
             set
             {
                 _Negozios = value;
                 RaisePropertyChanged("Negozio");
             }
         }


        Busta _Busta;
        public Busta Busta
        {
            get { return _Busta; }
            set
            {
                _Busta = value;
                RaisePropertyChanged("Busta");
            }
        }


        Negozio _Negozio;
        public Negozio Negozio
        {
            get { return _Negozio; }
            set
            {
                _Negozio = value;
                RaisePropertyChanged("Negozio");
            }
        }


        #region Command Object Declarations
       
        public RelayCommand<Busta> SaveCommand { get; set; }


        


       
        #endregion
        public MainViewModel(IDataAccessService servPxy)
        {
            _serviceProxy = servPxy;
            Busta = new Busta();
            Negozio = new Negozio();
             
            SaveCommand = new RelayCommand<Busta>(SalvaBusta);
            NegozioObser = new ObservableCollection<Negozio>();
            
        }
//Metodo Per Salvare La Busta
 void SalvaBusta(Busta Bus)
{
    Busta.BustaID = _serviceProxy.CreateBusta(Bus);
    if (Busta.BustaID != 0)
    {
        BustaOservable.Add(Busta);
        RaisePropertyChanged("Busta");
    }


       
        }
//Metodo Per Caricare I dati Della Combobox
 public void GetNegozio()
 {
     
     foreach (var item in _serviceProxy.GetNegozio())
     {
         NegozioObser.Add(item);
     }
 }
    }
}
Questa La View:

codice:
<Window x:Class="Prova1.View.MainWindow"        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        DataContext="{Binding Main,Source={StaticResource Locator}}"
        Title="MainWindow" Height="429" Width="615" Loaded="Window_Loaded">




    <Grid>
        <TextBox HorizontalAlignment="Left" Height="23" Margin="327,85,0,0" TextWrapping="Wrap" Text="{Binding Busta.BustaID, Mode=TwoWay}" VerticalAlignment="Top" Width="120"/>
        <Label Content="BustaID" HorizontalAlignment="Left" Margin="238,85,0,0" VerticalAlignment="Top"/>
        <Label Content="NegozioId" HorizontalAlignment="Left" Margin="238,116,0,0" VerticalAlignment="Top"/>
        <TextBox HorizontalAlignment="Left" Height="23" Margin="327,142,0,0" TextWrapping="Wrap" Text="{Binding Busta.NomeCliente, Mode=TwoWay}" VerticalAlignment="Top" Width="120"/>
        <Label Content="NomeCliente" HorizontalAlignment="Left" Margin="238,142,0,0" VerticalAlignment="Top"/>
        <Button Content="Salva" HorizontalAlignment="Left" Margin="215,233,0,0" VerticalAlignment="Top" Width="75"
                Command="{Binding SaveCommand}" CommandParameter="{Binding Busta}"/>
        <ComboBox HorizontalAlignment="Left" Margin="327,116,0,0" VerticalAlignment="Top" Width="120" ItemsSource="{Binding NegozioObser}" SelectedItem="{Binding Negozio}" IsSynchronizedWithCurrentItem="True">
            <ComboBox.ItemTemplate>
                <DataTemplate>
                    <Grid>
                        <TextBlock Text="{Binding RagioneSociale}"></TextBlock>
                    </Grid>
                </DataTemplate>
            </ComboBox.ItemTemplate>
        </ComboBox>
    </Grid>


</Window>