XAML: value of a textbox built into a listview and defined in a datatemplate

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DataTemplate

ListView

Hello, I am developing a UWP application for Windows 10.
I have embedded a textbox into a Listview, but I can't get the value of this textbox (probably due to the fact that the textbox is in a DataTemplate).
Thanks for helping me, this is my first UWA app (I was developing before in Silverlight), it's been several days since I've been looking for a solution on all forums, but I haven't found anything that works.

Here is an excerpt from my XAML:

<PivotItem Header="Favoris" Margin="0,0,0,0">
    <SemanticZoom Name="szFavoris" Height="500">
        <SemanticZoom.ZoomedInView>
            <ListView x:Name="listBoxobjFav" 
                        ItemsSource="{Binding Source={StaticResource cvsFavoris}}" 
                        BorderBrush="#FF141EE4"  Width="360" Height="495" Margin="0,10,0,0" VerticalAlignment="Top" 
                        IsItemClickEnabled="True" SelectionMode="Multiple" SelectionChanged="listBoxobjFav_SelectionChanged">
                <ListView.ItemTemplate>
                    <DataTemplate>
                        <Grid>
                            <Grid.ColumnDefinitions>
                                <ColumnDefinition Width="210" />
                                <ColumnDefinition Width="80" />
                            </Grid.ColumnDefinitions>

                            <TextBlock x:Name="NameTxt" Grid.Column="0" Margin="0,0,0,0" TextWrapping="Wrap" Text="{Binding Name}" FontSize="20" Foreground="White"/>
                            <TextBox Grid.Column="1" 
                                            x:Name="QteArt" 
                                            Text="{Binding QteArt, Mode=TwoWay}" 
                                            HorizontalAlignment="Right" 
                                            FontSize="16" 
                                            Foreground="DarkGray" 
                                            InputScope="Number" 
                                            Visibility="Visible"
                                            PlaceholderText="{Binding UniteMesure}"
                                            />      
                            <!-- this is the valueof  QteArt that I want retreive in my code behind -->
                        </Grid>
                    </DataTemplate>
                </ListView.ItemTemplate>

                <ListView.GroupStyle>
                    <GroupStyle>
                        <GroupStyle.HeaderTemplate>
                            <DataTemplate>
                                <TextBlock Text="{Binding Key}" Foreground="CadetBlue" FontSize="18" />
                            </DataTemplate>
                        </GroupStyle.HeaderTemplate>
                    </GroupStyle>
                </ListView.GroupStyle>

                <ListView.ItemContainerStyle>
                    <Style TargetType="ListViewItem">
                        <Setter Property="FocusVisualPrimaryBrush" Value="Transparent"/>
                    </Style>
                </ListView.ItemContainerStyle>

            </ListView>
        </SemanticZoom.ZoomedInView>

        <SemanticZoom.ZoomedOutView>
            <ListView x:Name="listBoxCatFav" SelectionMode="None" Width="360" Height="500" IsItemClickEnabled="True" BorderBrush="#FF141EE4" >
                <ListView.ItemTemplate>
                    <DataTemplate>
                        <StackPanel Orientation="Horizontal">
                            <TextBlock Margin="15,20,0,0" x:Name="CatTxt" Text="{Binding Group.Key}" TextWrapping="Wrap" Foreground="CadetBlue" FontSize="18"/>
                        </StackPanel>
                    </DataTemplate>
                </ListView.ItemTemplate>
            </ListView>
        </SemanticZoom.ZoomedOutView>
    </SemanticZoom>
</PivotItem>

What I have tried:

I have defined a UserControl, which contains the entire DataTemplate, but I am unable to embed this UserControl in the DataTemplate.