Numbered listbox

Question

I have a sorted listbox and need to display each item's row number. In this demo I have a Person class with a Name string property. The listbox displays a a list of Persons sorted by Name. How can I add to the datatemplate of the listbox the row number???

XAML:

<Window x:Class="NumberedListBox.Window1"     xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"     xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"     Height="300" Width="300">     <ListBox          ItemsSource="{Binding Path=PersonsListCollectionView}"          HorizontalContentAlignment="Stretch">         <ListBox.ItemTemplate>             <DataTemplate>                 <TextBlock Text="{Binding Path=Name}" />             </DataTemplate>         </ListBox.ItemTemplate>     </ListBox> </Window> 

Code behind:

using System; using System.Collections.ObjectModel; using System.Windows.Data; using System.Windows; using System.ComponentModel;  namespace NumberedListBox {     public partial class Window1 : Window     {         public Window1()         {             InitializeComponent();              Persons = new ObservableCollection<Person>();             Persons.Add(new Person() { Name = "Sally"});             Persons.Add(new Person() { Name = "Bob" });             Persons.Add(new Person() { Name = "Joe" });             Persons.Add(new Person() { Name = "Mary" });              PersonsListCollectionView = new ListCollectionView(Persons);             PersonsListCollectionView.SortDescriptions.Add(new SortDescription("Name", ListSortDirection.Ascending));              DataContext = this;         }          public ObservableCollection<Person> Persons { get; private set; }         public ListCollectionView PersonsListCollectionView { get; private set; }     }      public class Person     {         public string Name { get; set; }     } } 

Answer 1

Finally! If found a way much more elegant and probably with better performance either. (see also Accessing an ItemsControl item as it is added)

We "misuse" the property ItemsControl.AlternateIndex for this. Originally it is intended to handle every other row within a ListBox differently. (see http://msdn.microsoft.com/en-us/library/system.windows.controls.itemscontrol.alternationcount.aspx)

1. Set AlternatingCount to the amount of items contained in the ListBox

<ListBox ItemsSource="{Binding Path=MyListItems}"          AlternationCount="{Binding Path=MyListItems.Count}"          ItemTemplate="{StaticResource MyItemTemplate}" ... /> 

2. Bind to AlternatingIndex your DataTemplate

<DataTemplate x:Key="MyItemTemplate" ... >     <StackPanel>         <Label Content="{Binding RelativeSource={RelativeSource TemplatedParent}, Path=TemplatedParent.(ItemsControl.AlternationIndex)}" />         ...     </StackPanel> </DataTemplate> 

So this works without a converter, an extra CollectionViewSource and most importantly without brute-force-searching the source collection.

Answer 2

This should get you started:

http://weblogs.asp.net/hpreishuber/archive/2008/11/18/rownumber-in-silverlight-datagrid-or-listbox.aspx

It says it's for Silverlight, but I don't see why it wouldn't work for WPF. Basically, you bind a TextBlock to your data and use a custom value converter to output the current item's number.