BarChart Values not updating - wpf

Question

I am trying to develop a application where-in I a want to generate a random number after every three seconds, insert that number into a listBox and using DataTemplate display the ListBox as a rectangle.
This is for reference.
Now the problem is that I have used a DispatcherTimer which 'ticks' after 3 seconds but the rectangle is not updated.
I am posting my XAML and .cs code. Any hints ?
namespace ListBarGraph
{
/// <summary>
/// Interaction logic for MainWindow.xaml
/// </summary>
public partial class MainWindow : Window
{
DispatcherTimer dt = new DispatcherTimer();
DataFactory df = new DataFactory();
public MainWindow()
{
InitializeComponent();
dt.Tick += new EventHandler(dt_Tick);
dt.Interval = new TimeSpan(0, 0, 3);
dt.Start();
this.PreviewKeyDown += new KeyEventHandler(MainWindow_PreviewKeyDown);
}
void dt_Tick(object sender, EventArgs e)
{
df.GetData();
}
}
public class DataFactory
{
int number = 0;
public IEnumerable<int> GetData()
{
Random random = new Random();
number = random.Next(0, 100);
return new int[] { 0, number };
}
}
}
<Window x:Class="ListBarGraph.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="clr-namespace:ListBarGraph"
Title="MainWindow" Height="350" Width="525">
<Window.Resources>
<ObjectDataProvider x:Key="someData" ObjectType="{x:Type local:DataFactory}" MethodName="GetData" />
<DataTemplate x:Key="BarChartItemsTemplate">
<Border Width="300" Height="50">
<Grid>
<Rectangle Fill="Red" StrokeThickness="2" Height="40" Width="{Binding}" HorizontalAlignment="Right" VerticalAlignment="Bottom">
<Rectangle.LayoutTransform>
<ScaleTransform ScaleX="1.5"/>
</Rectangle.LayoutTransform>
</Rectangle>
</Grid>
</Border>
</DataTemplate>
<ItemsPanelTemplate x:Key="BarChartItemsPanel">
<VirtualizingStackPanel IsItemsHost="True">
<VirtualizingStackPanel.LayoutTransform>
<TransformGroup>
<RotateTransform Angle="90"/>
<ScaleTransform ScaleX="-1" ScaleY="1"/>
</TransformGroup>
</VirtualizingStackPanel.LayoutTransform>
</VirtualizingStackPanel>
</ItemsPanelTemplate>
</Window.Resources>
<Grid>
<ListBox ItemsSource="{Binding Source={StaticResource someData}}" ItemTemplate="{DynamicResource BarChartItemsTemplate}" ItemsPanel="{DynamicResource BarChartItemsPanel}"/>
</Grid>
</Window>

Answer 1

Your XAML is bound to one instance of DataFactory as created by the ObjectProvider, whilst your code-behind creates another instance altogether, to which the UI is not bound.
Try this to get you started. In your XAML, remove the ObjectProvider and change your ListBox to:
<ListBox ItemsSource="{Binding}" ...
Inside dt_Tick, do this:
this.DataContext = df.GetData();