Wpf - Xaml : Binding a list of TextBox in a List of String to Source

I want to create a list of TextBox in binding with ObservableCollection<String> in a ViewModel but i have a problem. The binding performs only by source to dialog but it not works by dialog to source

in my ViewModel i have

   private ObservableCollection<String> _ListSashDim;

    public ObservableCollection<String> ListSashDim
    {
        get { return _ListSashDim; }
        set {
            if (_ListSashDim != value)
            {
                _ListSashDim = value;
                this.RaisePropertyChanged("ListSashDim");
            }
        }

    }

the list is initialized as below

  private ObservableCollection<string> createListSashPosition(int numAnte)
    {
        ObservableCollection<string> ls = new ObservableCollection<string>();
        for (int i = 0; i < numAnte; i++)
        {
            ls.Add("X");
        }

        return ls;
    }

in my Xaml i have a DataTemplate

 <!--#region DataTemplate ListSashDim-->
    <DataTemplate x:Key="DataTemplateSashDim">
        <ItemsControl>
            <StackPanel Orientation="Vertical" Width="116" HorizontalAlignment="Center" VerticalAlignment="Center">
                <TextBlock FontSize="10" HorizontalAlignment="Center" Text="Sash Dim"></TextBlock>
                <TextBox x:Name="tbSashDim" Width="90" Text="{Binding Path=.,Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}" ></TextBox>
            </StackPanel>
        </ItemsControl>
    </DataTemplate>
    <!--#endregion-->

and an ItemsControl in a StackPanel

<StackPanel   
                Orientation="Horizontal" 
                HorizontalAlignment="Center" 
                VerticalAlignment="Center" FlowDirection="LeftToRight"
                  Margin="0,10,0,0">

                <ItemsControl ItemsSource="{Binding ListSashDim, UpdateSourceTrigger=PropertyChanged, Mode=TwoWay}" 
                              HorizontalAlignment="Center" 
                              VerticalAlignment="Center" 
                              Margin="0" ItemTemplate="{DynamicResource DataTemplateSashDim}" Padding="8" >
                    <ItemsControl.ItemsPanel>
                        <ItemsPanelTemplate>
                            <StackPanel Orientation="Horizontal" HorizontalAlignment="Center"></StackPanel>
                        </ItemsPanelTemplate>
                    </ItemsControl.ItemsPanel>
                </ItemsControl>
            </StackPanel>

Thanks so much Manuel