اجرا نشدن Relay Command

[niloo17]

با سلام ...
یک ویو مربوط به ثبت master-detail دارم که گرید مربوط به detail در constructor پر میشه و با زدن دکمه اضافه ایتم ها باید اضافه بشه

  /// <summary>

        /// Collection of Image.

        /// </summary>

        ICollectionView _imageCollection;



        public ICollectionView ImageCollection

        {

            get { return _imageCollection; }

            set

            {

                if (value != _imageCollection)

                {

                    _imageCollection = value;

                    RaisePropertyChanged("ImageCollection");

                }

            }

        }









        private List<PurchaseInvoiceDetail> _listDetail = new List<PurchaseInvoiceDetail>();



 public PurchaseInvoiceDetailViewModel(PurchaseInvoice item)

        {

            CustomerCollection = CollectionViewSource.GetDefaultView(_db.Customers.  ToList());

            GoodsCollection = CollectionViewSource.GetDefaultView(_db.Goods.ToLi  st());



            AddCommand = new RelayCommand(() =>

            {

                if (GoodsId != 0 && Price != 0 && Count != 0)

                {

                    var goods = _db.Goods.Find(GoodsId);



                    _listDetail.Add(new PurchaseInvoiceDetail() { GoodsId = GoodsId, Goods = goods, Count = Count, Price = Price, Id = 0, PurchaseInvoiceId = 0 });

                    CollectionViewSource.GetDefaultView(_listDetail).R  efresh();

                    ImageCollection = CollectionViewSource.GetDefaultView(_listDetail);

                    GoodsId = 0;

                    Price = 0;

                    Count = 0;

                }



            });





            if (item != null)

            {

                Number = item.Number;

                CustomerId = item.CustomerId;

                Date = new PersianDate((DateTime)item.Date);

                _purchaseInvoice = item.Id;

                _listDetail = _db.PurchaseInvoiceDetails.Include("Goods").Where(  m => m.PurchaseInvoiceId == item.Id).ToList();

                CollectionViewSource.GetDefaultView(_listDetail).R  efresh();

                ImageCollection = CollectionViewSource.GetDefaultView(_listDetail);

            }

و در ویو

    <DataGrid   CellStyle="{StaticResource MaterialDesignDataGridCell}"  Name="ListView" 

                           IsReadOnly="True" BorderBrush="{DynamicResource MaterialDesignDivider}"  

                           BorderThickness="1"    Height="250"  Margin="0"   AutoGenerateColumns="False"   

                           ItemsSource="{Binding ImageCollection,NotifyOnSourceUpdated=True,Mode=On  eWay}" 

                >

                    <DataGrid.Columns>

                      

                        <DataGridTextColumn Header="نام کالا" Binding="{Binding Path=Goods.Name}" Width="300"/>



                        <DataGridTextColumn Binding="{Binding Path=Count}" Width="150"

                                            Header="تعداد"/>

                        <DataGridTextColumn Header="قیمت" Binding="{Binding Path=Price}" Width="*"/>

                    </DataGrid.Columns>

                    <DataGrid.InputBindings>

                        <KeyBinding 

                            Key="Delete"

                            Command="{Binding DeleteCommand}" CommandParameter="{Binding SelectedIndex, ElementName=ListView}"/>



                    </DataGrid.InputBindings>

                </DataGrid>



  <Button   Command="{Binding AddCommand}" Margin="0 7 3 0"

                        Content="{materialDesign:PackIcon Plus}"

                      Width="45"   ToolTip="اضافه" />

ولی relay command مربوط به دکمه اضافه اجرا نمیشه!!!