By default, a VirtualizingStackPanel creates an item container for each visible item and discards it when it is no longer needed (such as when the item is scrolled out of view). When an ItemsControl contains a many items, the process of creating and discarding item containers can negatively affect performance. When VirtualizationMode()()() is set to Recycling, the VirtualizingStackPanel reuses item containers instead of creating a new one each time.

When VirtualizingStackPanel cannot recycle item containers, it uses the standard mode of virtualization, which is to create and discard item containers for each item. The following list describes cases when the VirtualizingStackPanel cannot recycle item containers:

• The ItemsControl contains item containers of different types. For example, a Menu might have items that use both MenuItem and Seperator objects as the item containers.

• You explicitly create the item containers for the ItemsControl. For more information about explicitly versus implicitly creating item containers, see the "Item Container Classes" section in Controls Content Model Overview.

The following example creates a ListBox and sets the VirtualizationMode()()() attached property to Recycling.

<StackPanel>

  <StackPanel.Resources>
    <src:LotsOfItems x:Key="data"/>
  </StackPanel.Resources>

  <ListBox Height="150" ItemsSource="{StaticResource data}" 
             VirtualizingStackPanel.VirtualizationMode="Recycling" />

</StackPanel>

The following example shows the data used in the previous example.

Public Class LotsOfItems
    Inherits ObservableCollection(Of String)
    Public Sub New()
        For i As Integer = 0 To 999
            Add("item " & i.ToString())
        Next
    End Sub
End Class

public class LotsOfItems : ObservableCollection<String>
{
    public LotsOfItems()
    {
        for (int i = 0; i < 1000; ++i)
        {
            Add("item " + i.ToString());
        }
    }
}

Windows 7, Windows Vista, Windows XP SP2, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003

.NET Framework

Reference