Here’s my ListBox:

<ListBox x:Name="Difetti"
         ItemsSource="{Binding Difetti}"
         HorizontalAlignment="Left"
         VerticalAlignment="Top"
         Margin="20,40,0,0"
         Width="700"
         Height="350"
         Grid.Row="2"
         Grid.ColumnSpan="3">
    <ListBox.ItemsPanel>
        <ItemsPanelTemplate>
            <WrapPanel Orientation="Horizontal" />
        </ItemsPanelTemplate>
    </ListBox.ItemsPanel>
    <ListBox.ItemTemplate>
        <DataTemplate>
            <StackPanel>
                <TextBox x:Name="Metro"
                         controls:TextBoxHelper.Watermark="Metro"
                         PreviewTextInput="validateMaskDecimal">
                    <TextBox.Text>
                        <Binding Path="Metro">
                        </Binding>
                    </TextBox.Text>
                </TextBox>
                <ComboBox x:Name="Grado"
                          ItemsSource="{Binding ListGradi}"
                          DisplayMemberPath="DisplayValue"
                          SelectedValuePath="Value"
                          SelectedValue="{Binding Grado}"
                          controls:TextBoxHelper.Watermark="Grado" />
            </StackPanel>
        </DataTemplate>
    </ListBox.ItemTemplate>
</ListBox>

Which using a button I increase basically this way (empty record):

Difetto difetto = new Difetto();
data.Difetti.Add(difetto);

Once added, is there any PreviewAddItem event? I need to set carefully the Watermark on each element, due to the current/selected language.

When I switch language, I iterate on each ListBox item’s doing somethings like this:

 Utilities.FindVisualChild<TextBox>(listBoxItem, "Metro")?.SetValue(TextBoxHelper.WatermarkProperty, resourceManager?.GetString("Metro"));
 Utilities.FindVisualChild<ComboBox>(listBoxItem, "Grado")?.SetValue(TextBoxHelper.WatermarkProperty, resourceManager?.GetString("Grado"));

But on create, I won’t to iterate the existing items only for set the new records. Is there somethings like this event? Or maybe I can get the ListBoxItem immediately after data.Difetti.Add(difetto) before its being rendered on the UI?

For completeness, here’s the FindVisualChild method:

public static T? FindVisualChild<T>(DependencyObject parent, string name) where T : FrameworkElement
{
    for (int i = 0; i < VisualTreeHelper.GetChildrenCount(parent); i++)
    {
        DependencyObject child = VisualTreeHelper.GetChild(parent, i);
        if (child != null && child is T && ((T)child).Name == name)
        {
            return (T)child;
        }
        else if (child != null)
        {
            T? childOfChild = FindVisualChild<T>(child, name);
            if (childOfChild != null)
            {
                return childOfChild;
            }
        }
    }

    return null;
}