Binding in WPF to element of array specified by property

Question

Say I've got some TextBlocks on my UI, something like so:

<StackPanel Orientation="Vertical">     <TextBlock Text="{Binding DessertIndex}" />     <TextBlock Text="{Binding Food[2]}" />     <TextBlock Text="{Binding Food[{Binding DessertIndex}]}" /> </StackPanel> 

and in my code behind I've got something like this:

public partial class MainWindow : Window {     public int DessertIndex     {         get { return 2; }     }      public object[] Food     {         get         {             return new object[]{"liver", "spam", "cake", "garlic" };         }     }      public MainWindow()     {         InitializeComponent();         DataContext = this;     } } 

The first two TextBlocks display fine for me, displaying 2 and 'cake' respectively. The third one doesn't accomplish what I'd like, namely use the DessertIndex property to index into that array and also display 'cake'. I did a little searching here on SO for a similar question but didn't find one. Ultimately, I don't want to specify values like 2 in my .xaml file and would like to rely upon a property instead for indexing into that array. Is this possible? If so, what am I doing wrong here?

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EDIT:

So what I more closely have is a situation where the data is a List of these object[] and I'm using the above StackPanel as part of a DataTemplate for a ListBox. So the idea, as Mark Heath suggests below, of using a property that dereferences the array doesn't seem to work as I'd want. Ideas?

Answer 1

Another alternative is to use MultiBinding with a converter:

<Window x:Class="WpfApplication1.MainWindow"         xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"         xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"         xmlns:local="clr-namespace:WpfApplication1"         Title="MainWindow" Height="350" Width="525">     <StackPanel Orientation="Vertical">         <StackPanel.Resources>             <local:FoodIndexConverter x:Key="foodIndexConverter" />         </StackPanel.Resources>         <TextBlock Text="{Binding DessertIndex}" />         <TextBlock Text="{Binding Food[2]}" />         <TextBlock>             <TextBlock.Text>                 <MultiBinding Converter="{StaticResource foodIndexConverter}">                     <Binding Path="DessertIndex" />                     <Binding Path="Food"/>                 </MultiBinding>             </TextBlock.Text>         </TextBlock>     </StackPanel> </Window> 

Then in the code-behind, the converter is defined something like this:

namespace WpfApplication1 {     public class FoodIndexConverter : IMultiValueConverter     {         public object Convert(object[] values, Type targetType, object parameter, System.Globalization.CultureInfo culture)         {             if (values == null || values.Length != 2)                 return null;              int? idx = values[0] as int?;             object[] food = values[1] as object[];              if (!idx.HasValue || food == null)                 return null;              return food[idx.Value];         }          public object[] ConvertBack(object value, Type[] targetTypes, object parameter, System.Globalization.CultureInfo culture)         {             throw new NotImplementedException();         }     } }