Question

here’s the code. All it does is, it creates a new ListBox control inside a StackPanel and adds to it a new Item. The problem is described at the bottom of the page.

MyWindow.xaml

<Window.Resources>
    <DataTemplate x:Key="itemsTemplate">
        <Border Width="200" Height="50" >
            <ListBox ItemsSource="{Binding Title}" />
        </Border>
    </DataTemplate>
</Window.Resources>

<Grid>
    <Grid.ColumnDefinitions>
        <ColumnDefinition Width="100"/>
        <ColumnDefinition Width="*"/>
    </Grid.ColumnDefinitions>

    <ItemsControl Grid.Column="1"
                  Grid.Row="0"
                  ItemsSource="{Binding ElementName=mainWindow, Path=DataItems}"
                  ItemTemplate="{StaticResource itemsTemplate}">
        <ItemsControl.Template>
            <ControlTemplate>
                <ScrollViewer HorizontalScrollBarVisibility="Auto">
                    <ItemsPresenter />
                </ScrollViewer>
            </ControlTemplate>
        </ItemsControl.Template>
        <ItemsControl.ItemsPanel>
            <ItemsPanelTemplate>
                <StackPanel Orientation="Horizontal" />
            </ItemsPanelTemplate>
        </ItemsControl.ItemsPanel>
    </ItemsControl>
</Grid>

MyWindow.xaml.cs

    private ObservableCollection<MyDataItem> dataItems;

    public ObservableCollection<MyDataItem> DataItems
    {
        get { return dataItems; }
    }

    public Window1()
    {
        dataItems = new ObservableCollection<MyDataItem>();
        InitializeComponent();
    }

MyDataItem.cs

public class MyDataItem : DependencyObject
{
    public string Title
    {
        get
        {
            return (string)GetValue(TitleProperty);
        }
        set
        {
            SetValue(TitleProperty, value);
        }
    }

    public static readonly DependencyProperty TitleProperty =
        DependencyProperty.Register("Title", typeof(string), 
                                    typeof(MyDataItem), new UIPropertyMetadata(""));

    public MyDataItem(string title)
    {
        Title = title;
    }
}

Add a new Listbox with item

    void addNewItem_Click(object sender, RoutedEventArgs e)
    {
        MyDataItem item = new MyDataItem("12");
        dataItems.Add(item);
        e.Handled = true;
    }

after that action, I see that new ListBox control, but all its item’s characters are treated as a separate items as You can see @ the picture. Why ?

[ EDIT ]

solved, I had to change from string to List everywhere in that class:

public class MyDataItem : DependencyObject
{
    public List<string> Title
    {
        get
        {
            return (List<string>)GetValue(TitleProperty);
        }
        set
        {
            SetValue(TitleProperty, value);
        }
    }

    public static readonly DependencyProperty TitleProperty =
        DependencyProperty.Register("Title", typeof(string), 
                                    typeof(MyDataItem), 
                                    new UIPropertyMetadata(new List<string>()));

    public MyDataItem(List<string> title)
    {
        Title = title;
    }
}

Answer 1

Because you are giving data source as string.. it is converting that string to collection (character array) since itemssource property will always be collection..

if you still want to create a list box in data template with single item (in you case it is Title).. then try this..

Change you title property to List and while creating your title create a list which contains one string . so item source will be list and since itemssource contains one string it will create only one item.