TreeView is very slow with many loaded objects

Describe the bug With many objects loaded into the tree, scrolling and general application responsiveness are negatively affected

To Reproduce Steps to reproduce the behavior:

Load many objects with hierarchy into a TreeView. Expand all expandable nodes. Testing here with 5000 entries.

Expected behavior TreeView should be able to handle many entries (possibly via virtualization?)

Desktop (please complete the following information):

Tested on Windows 10 and RHEL 8

Additional context Tree objects look like this:

    public interface ITreeItem
    {
        public int          DatabaseId { get; set; }
        public bool         IsExpanded { get; set; }
        public bool         IsChecked  { get; set; }
        public string       Name       { get; set; }
        public List<string> Tags       { get; set; }
    }

    public class TreeEndpoint : ReactiveObject, ITreeItem
    {
        public            int          DatabaseId { get; set; }
        [Reactive] public bool         IsExpanded { get; set; }
        [Reactive] public bool         IsChecked  { get; set; }
        [Reactive] public string       Name       { get; set; }
        public            List<string> Tags       { get; set; }
    }

    public class TreeGroup : ReactiveObject, ITreeItem
    {
        public            int          DatabaseId { get; set; }
        [Reactive] public bool         IsExpanded { get; set; }
        [Reactive] public bool         IsChecked  { get; set; }
        [Reactive] public string       Name       { get; set; }
        public            List<string> Tags       { get; set; }

        [Reactive] public ObservableCollection<ITreeItem> Children { get; set; }
    }

TreeView bindings look like this:

                <TreeView Items="{Binding Items}"
                          SelectedItem="{Binding SelectedItem, Mode=TwoWay}"
                          ClipToBounds="True">
                    <TreeView.Styles>
                        <Style Selector="TreeViewItem">
                            <Setter Property="IsExpanded" Value="{Binding IsExpanded, Mode=TwoWay}"/>
                        </Style>
                    </TreeView.Styles>
                    <TreeView.DataTemplates>
                        <TreeDataTemplate DataType="treeDataStructures:TreeGroup"
                                          ItemsSource="{Binding Children}">
                            <VirtualizingStackPanel Classes="treeListItem"
                                        Orientation="Horizontal"
                                        ClipToBounds="True">
                                <CheckBox IsChecked="{Binding IsChecked, Mode=TwoWay}">
                                    <!-- <Interaction.Behaviors> -->
                                    <!--     <ButtonClickEventTriggerBehavior> -->
                                    <!--         <InvokeCommandAction Command="{Binding $parent[UserControl].DataContext.SetCheckedState}" -->
                                    <!--                              CommandParameter="{Binding}"/> -->
                                    <!--     </ButtonClickEventTriggerBehavior> -->
                                    <!-- </Interaction.Behaviors> -->
                                </CheckBox>
                                <TextBlock Foreground="Red" 
                                           Text="{Binding Name}" />
                            </VirtualizingStackPanel>
                        </TreeDataTemplate>
                        <DataTemplate DataType="treeDataStructures:TreeEndpoint">
                            <VirtualizingStackPanel Classes="treeListItem"
                                                    Orientation="Horizontal"
                                                    ClipToBounds="True">
                                <CheckBox IsChecked="{Binding IsChecked, Mode=TwoWay}"/>
                                <TextBlock Text="{Binding Name}" />
                            </VirtualizingStackPanel>
                        </DataTemplate>
                    </TreeView.DataTemplates>
                </TreeView>

[grokys]

@SCLDGit is this for a commercial application? Would you be willing to pay for a commercial control for this? If so we might have a solution.

[KvanTTT]

@SCLDGit Can you provide examples? I have never seen a case where so many items need to be loaded at once in a TreeView. Perhaps 3D/graphics software only?

Something like AST or parse tree exploring. For instance, https://astexplorer.net/ but offline.