RenderTransform flickering - silverlight

Question

See the following code,
After I clicked the button, the listbox render several times.
How can I prevent Listbox flickering?
Is it possible to tell a control stop update/render?
<UserControl x:Class="SilverlightApplication52.MainPage"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
mc:Ignorable="d"
d:DesignHeight="300"
d:DesignWidth="400">
<Grid x:Name="LayoutRoot"
Background="Gray"
HorizontalAlignment="Stretch"
VerticalAlignment="Stretch">
<ListBox x:Name="listbox"
Background="White"
Margin="100">
<ListBox.ItemsPanel>
<ItemsPanelTemplate>
<Canvas />
</ItemsPanelTemplate>
</ListBox.ItemsPanel>
<ListBox.ItemContainerStyle>
<Style TargetType="ListBoxItem">
</Style>
</ListBox.ItemContainerStyle>
<ListBox.ItemTemplate>
<DataTemplate>
<Rectangle Width="{Binding Width}"
Height="{Binding Height}"
Fill="{Binding Background}"
RenderTransformOrigin="0.5,0.5">
<Rectangle.RenderTransform>
<TransformGroup>
<ScaleTransform ScaleX="{Binding Scale}"
ScaleY="{Binding Scale}" />
<RotateTransform Angle="{Binding Angle}" />
<TranslateTransform X="{Binding Left}"
Y="{Binding Top}" />
</TransformGroup>
</Rectangle.RenderTransform>
</Rectangle>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
<Button Content="test"
Width="50"
Height="50"
Click="Button_Click" />
</Grid>
public partial class MainPage : UserControl
{
public class ItemInfo
{
public double Left { get; set; }
public double Top { get; set; }
public double Width { get; set; }
public double Height { get; set; }
public double Angle { get; set; }
public double Scale { get; set; }
public Brush Background { get; set; }
}
ObservableCollection<ItemInfo> _items = new ObservableCollection<ItemInfo>();
public MainPage()
{
InitializeComponent();
listbox.ItemsSource = _items;
}
Random random = new Random();
private void Button_Click(object sender, RoutedEventArgs e)
{
_items.Clear();
for (int i = 0; i < 2000; i++)
{
byte r = (byte)(random.NextDouble()*255);
byte g = (byte)(random.NextDouble()*255);
byte b = (byte)(random.NextDouble()*255);
_items.Add(
new ItemInfo
{
Left = random.NextDouble() * 500,
Top = random.NextDouble() * 500,
Width = random.NextDouble() * 1000,
Height = random.NextDouble() * 1000,
Angle = random.NextDouble() * 359,
Scale = random.NextDouble() * 1,
Background = new SolidColorBrush(Color.FromArgb(255,r,g,b)),
}
);
}
}
}

Answer 1

Try adding to a separate ObservableCollection in that loop (that is not referenced/bound to the listbox). Then when the loop is done assign the listbox ItemsSource to the new observablecollection.