WPF ScrollViewer virtualization AND smooth scroll. Full: https://github.com/PiN73/TestScrollVirtualization/

!.md

By default, <ItemsControl>/<ScrollViewer> doesn't use virtualization. All its items are rendered at once. This causes lags/freezing on first render and each re-render (for example, if list data or window size changes).

Adding ScrollViewer.CanContentScroll="True" will enable virtualization and make loading fast. But the list will be scrolled one whole item a time, which feels like jumping if items height is big enough.

To make virtualization enabled and keep smooth scrolling, add also VirtualizingPanel.ScrollUnit="Pixel"

.cs

InitializeComponent();
MyButton.Click += (s, e) =>
{
    MyButton.Visibility = Visibility.Collapsed;
    MyItemsControl.ItemsSource = Enumerable
        .Range(0, 10000)
        .Select(i => $"Item {i}")
        .ToArray();
};

.xaml

<Grid>
    <ItemsControl Name="MyItemsControl"
                  ScrollViewer.CanContentScroll="True"
                  VirtualizingPanel.ScrollUnit="Pixel"
                  VirtualizingStackPanel.VirtualizationMode="Recycling">

        <ItemsControl.ItemsPanel>
            <ItemsPanelTemplate>
                <VirtualizingStackPanel />
            </ItemsPanelTemplate>
        </ItemsControl.ItemsPanel>

        <ItemsControl.Template>
            <ControlTemplate>
                <ScrollViewer>
                    <ItemsPresenter/>
                </ScrollViewer>
            </ControlTemplate>
        </ItemsControl.Template>

        <ItemsControl.ItemTemplate>
            <DataTemplate>
                <TextBlock FontSize="64" Text="{Binding}" />
            </DataTemplate>
        </ItemsControl.ItemTemplate>
    </ItemsControl>

    <Button Name="MyButton">Show List</Button>
</Grid>

You have saved my day with this! Thanks

With my ListBox, if I want to enable virtualization, I have to set Template, but if I want smooth scrolling, I have to go back to the ListBox to set it, which is weird.