Personalización de TreeView para permitir la selección múltiple

Question

El control TreeView WPF incorporado no permite la selección múltiple, como lo hace un ListBox. ¿Cómo puedo personalizar TreeView para permitir la selección múltiple sin reescribirlo?

Answer 1

Cuando considero anular el comportamiento fundamental de un control, como una vista en árbol, siempre me gusta considerar la usabilidad y el esfuerzo asociados con mi decisión.

En el caso específico de una vista en árbol, encuentro que cambiar a una vista de lista en combinación con cero, uno o más controles hace que la solución sea más útil y, a menudo, más fácil de implementar.

Como ejemplo, considere el diálogo Abrir común, o la aplicación Windows Explorer.

Answer 2

He simplificado esta tarea agregando una casilla de verificación antes del texto para cada elemento treeviewitem.

Así que he creado un dockpanel con 2 elementos dentro: checkbox + textblock.

Entonces ...

XAML

<TreeView x:Name="treeViewProcesso" Margin="1,30.351,1,5" BorderBrush="{x:Null}" MinHeight="250" VerticalContentAlignment="Top" BorderThickness="0" > 
    <TreeViewItem Header="Documents" x:Name="treeView" IsExpanded="True" DisplayMemberPath="DocumentsId" >    
    </TreeViewItem> 
</TreeView> 

CS

TreeViewItem treeViewItem = new TreeViewItem(); 
DockPanel dp = new DockPanel(); 
CheckBox cb = new CheckBox(); 
TextBlock tb = new TextBlock(); 
tb.Text = "Item"; 
dp.Children.Add(cb); 
dp.Children.Add(tb); 
treeViewItem.Header = dp; 
treeViewItem.Selected += new RoutedEventHandler(item_Selected); 
treeView.Items.Add(treeViewItem); 

Y entonces se puede acceder valor casilla:

void item_Selected(object sender, RoutedEventArgs e) 
{ 
    selectedTVI = ((TreeViewItem)sender); 

    CheckBox cb = (Checkbox)((DockPanel)selectedTVI.Header).Children[0]; 
} 

Esta es una forma sencilla de hacerlo si no necesita algo complejo.

Answer 3

Finalmente terminé de codificar mi propio CustomControl que contenía un TreeView dentro. Basado en el trabajo de otros la clave de la funcionalidad reside en hacer que todos los elementos del modelo del TreeView heredar la interfaz ISelectable:

public interface ISelectable 
{ 
    public bool IsSelected {get; set} 
} 

De esta manera tendremos una nueva propiedad 'IsSelected' que no tiene nada que hacer con TreeViewItem IsSelected. Solo tenemos que diseñar nuestro árbol para que maneje la propiedad IsSelected del modelo. Aquí el código (se trata de utilizar las bibliotecas de arrastrar & disponibles en http://code.google.com/p/gong-wpf-dragdrop/):

XAML

<UserControl x:Class="Picis.Wpf.Framework.ExtendedControls.TreeViewEx.TreeViewEx" 

     xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" 
     xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" 
     xmlns:DragAndDrop="clr-namespace:Picis.Wpf.Framework.DragAndDrop"> 

<TreeView ItemsSource="{Binding ItemsSource, RelativeSource={RelativeSource AncestorType=UserControl}}" 
      ItemTemplate="{Binding ItemTemplate, RelativeSource={RelativeSource AncestorType=UserControl}}" 
      ItemContainerStyle="{Binding ItemContainerStyle, RelativeSource={RelativeSource AncestorType=UserControl}}" 
      DragAndDrop:DragDrop.DropHandler ="{Binding DropHandler, RelativeSource={RelativeSource AncestorType=UserControl}}" 
      PreviewMouseDown="TreeViewOnPreviewMouseDown" 
      PreviewMouseUp="TreeViewOnPreviewMouseUp" 
      x:FieldModifier="private" x:Name="InnerTreeView" > 
    <TreeView.Resources> 
     <Style TargetType="TreeViewItem"> 
      <Style.Resources> 
       <SolidColorBrush x:Key="{x:Static SystemColors.HighlightBrushKey}" Color="White" /> 
       <SolidColorBrush x:Key="{x:Static SystemColors.HighlightTextBrushKey}" Color="Black" /> 
       <SolidColorBrush x:Key="{x:Static SystemColors.ControlBrushKey}" Color="White" /> 
      </Style.Resources> 
     </Style> 
    </TreeView.Resources> 
</TreeView> 

C#:

using System.Collections.Generic; 
using System.Linq; 
using System.Windows; 
using System.Windows.Controls; 
using System.Windows.Input; 
using System.Windows.Media; 
using System.Windows.Shapes; 
using GongSolutions.Wpf.DragDrop; 
using DragDrop = GongSolutions.Wpf.DragDrop; 

namespace <yournamespace>.TreeViewEx 
{ 
public partial class TreeViewEx : UserControl 
{ 
    #region Attributes 

    private TreeViewItem _lastItemSelected; // Used in shift selections 
    private TreeViewItem _itemToCheck; // Used when clicking on a selected item to check if we want to deselect it or to drag the current selection 
    private bool _isDragEnabled; 
    private bool _isDropEnabled; 

    #endregion 

    #region Dependency Properties 

    public static readonly DependencyProperty ItemsSourceProperty = DependencyProperty.Register("ItemsSource", typeof(IEnumerable<ISelectable>), typeof(TreeViewEx)); 

    public IEnumerable<ISelectable> ItemsSource 
    { 
     get 
     { 
      return (IEnumerable<ISelectable>)this.GetValue(TreeViewEx.ItemsSourceProperty); 
     } 
     set 
     { 
      this.SetValue(TreeViewEx.ItemsSourceProperty, value); 
     } 
    } 

    public static readonly DependencyProperty ItemTemplateProperty = DependencyProperty.Register("ItemTemplate", typeof(DataTemplate), typeof(TreeViewEx)); 

    public DataTemplate ItemTemplate 
    { 
     get 
     { 
      return (DataTemplate)GetValue(TreeViewEx.ItemTemplateProperty); 
     } 
     set 
     { 
      SetValue(TreeViewEx.ItemTemplateProperty, value); 
     } 
    } 

    public static readonly DependencyProperty ItemContainerStyleProperty = DependencyProperty.Register("ItemContainerStyle", typeof(Style), typeof(TreeViewEx)); 

    public Style ItemContainerStyle 
    { 
     get 
     { 
      return (Style)GetValue(TreeViewEx.ItemContainerStyleProperty); 
     } 
     set 
     { 
      SetValue(TreeViewEx.ItemContainerStyleProperty, value); 
     } 
    } 

    public static readonly DependencyProperty DropHandlerProperty = DependencyProperty.Register("DropHandler", typeof(IDropTarget), typeof(TreeViewEx)); 

    public IDropTarget DropHandler 
    { 
     get 
     { 
      return (IDropTarget)GetValue(TreeViewEx.DropHandlerProperty); 
     } 
     set 
     { 
      SetValue(TreeViewEx.DropHandlerProperty, value); 
     } 
    } 

    #endregion 

    #region Properties 

    public bool IsDragEnabled 
    { 
     get 
     { 
      return _isDragEnabled; 
     } 
     set 
     { 
      if (_isDragEnabled != value) 
      { 
       _isDragEnabled = value; 
       DragDrop.SetIsDragSource(this.InnerTreeView, _isDragEnabled); 
      } 
     } 
    } 

    public bool IsDropEnabled 
    { 
     get 
     { 
      return _isDropEnabled; 
     } 
     set 
     { 
      if (_isDropEnabled != value) 
      { 
       _isDropEnabled = value; 
       DragDrop.SetIsDropTarget(this.InnerTreeView, _isDropEnabled); 
      } 
     } 
    } 

    #endregion 

    #region Public Methods 

    public TreeViewEx() 
    { 
     InitializeComponent(); 
    } 

    #endregion 

    #region Event Handlers 

    private void TreeViewOnPreviewMouseDown(object sender, MouseButtonEventArgs e) 
    { 
     if (e.OriginalSource is Shape || e.OriginalSource is Grid || e.OriginalSource is Border) // If clicking on the + of the tree 
      return; 

     TreeViewItem item = this.GetTreeViewItemClicked((FrameworkElement)e.OriginalSource); 

     if (item != null && item.Header != null) 
     { 
      this.SelectedItemChangedHandler(item); 
     } 
    } 

    // Check done to avoid deselecting everything when clicking to drag 
    private void TreeViewOnPreviewMouseUp(object sender, MouseButtonEventArgs e) 
    { 
     if (_itemToCheck != null) 
     { 
      TreeViewItem item = this.GetTreeViewItemClicked((FrameworkElement)e.OriginalSource); 

      if (item != null && item.Header != null) 
      { 
       if (!TreeViewEx.IsCtrlPressed) 
       { 
        GetTreeViewItems(true).Select(t => t.Header).Cast<ISelectable>().ToList().ForEach(f => f.IsSelected = false); 
        ((ISelectable)_itemToCheck.Header).IsSelected = true; 
        _lastItemSelected = _itemToCheck; 
       } 
       else 
       { 
        ((ISelectable)_itemToCheck.Header).IsSelected = false; 
        _lastItemSelected = null; 
       } 
      } 
     } 
    } 

    #endregion 

    #region Private Methods 

    private void SelectedItemChangedHandler(TreeViewItem item) 
    { 
     ISelectable content = (ISelectable)item.Header; 

     _itemToCheck = null; 

     if (content.IsSelected) 
     { 
      // Check it at the mouse up event to avoid deselecting everything when clicking to drag 
      _itemToCheck = item; 
     } 
     else 
     { 
      if (!TreeViewEx.IsCtrlPressed) 
      { 
       GetTreeViewItems(true).Select(t => t.Header).Cast<ISelectable>().ToList().ForEach(f => f.IsSelected = false); 
      } 

      if (TreeViewEx.IsShiftPressed && _lastItemSelected != null) 
      { 
       foreach (TreeViewItem tempItem in GetTreeViewItemsBetween(_lastItemSelected, item)) 
       { 
        ((ISelectable)tempItem.Header).IsSelected = true; 
        _lastItemSelected = tempItem; 
       } 
      } 
      else 
      { 
       content.IsSelected = true; 
       _lastItemSelected = item; 
      } 
     } 
    } 

    private static bool IsCtrlPressed 
    { 
     get 
     { 
      return Keyboard.IsKeyDown(Key.LeftCtrl) || Keyboard.IsKeyDown(Key.RightCtrl); 
     } 
    } 

    private static bool IsShiftPressed 
    { 
     get 
     { 
      return Keyboard.IsKeyDown(Key.LeftShift) || Keyboard.IsKeyDown(Key.RightShift); 
     } 
    } 

    private TreeViewItem GetTreeViewItemClicked(UIElement sender) 
    { 
     Point point = sender.TranslatePoint(new Point(0, 0), this.InnerTreeView); 
     DependencyObject visualItem = this.InnerTreeView.InputHitTest(point) as DependencyObject; 
     while (visualItem != null && !(visualItem is TreeViewItem)) 
     { 
      visualItem = VisualTreeHelper.GetParent(visualItem); 
     } 

     return visualItem as TreeViewItem; 
    } 

    private IEnumerable<TreeViewItem> GetTreeViewItemsBetween(TreeViewItem start, TreeViewItem end) 
    { 
     List<TreeViewItem> items = this.GetTreeViewItems(false); 

     int startIndex = items.IndexOf(start); 
     int endIndex = items.IndexOf(end); 

     // It's possible that the start element has been removed after it was selected, 
     // I don't find a way to happen on the end but I add the code to handle the situation just in case 
     if (startIndex == -1 && endIndex == -1) 
     { 
      return new List<TreeViewItem>(); 
     } 
     else if (startIndex == -1) 
     { 
      return new List<TreeViewItem>() {end}; 
     } 
     else if (endIndex == -1) 
     { 
      return new List<TreeViewItem>() { start }; 
     } 
     else 
     { 
      return startIndex > endIndex ? items.GetRange(endIndex, startIndex - endIndex + 1) : items.GetRange(startIndex, endIndex - startIndex + 1); 
     } 
    } 

    private List<TreeViewItem> GetTreeViewItems(bool includeCollapsedItems) 
    { 
     List<TreeViewItem> returnItems = new List<TreeViewItem>(); 

     for (int index = 0; index < this.InnerTreeView.Items.Count; index++) 
     { 
      TreeViewItem item = (TreeViewItem)this.InnerTreeView.ItemContainerGenerator.ContainerFromIndex(index); 
      returnItems.Add(item); 
      if (includeCollapsedItems || item.IsExpanded) 
      { 
       returnItems.AddRange(GetTreeViewItemItems(item, includeCollapsedItems));      
      } 
     } 

     return returnItems; 
    } 

    private static IEnumerable<TreeViewItem> GetTreeViewItemItems(TreeViewItem treeViewItem, bool includeCollapsedItems) 
    { 
     List<TreeViewItem> returnItems = new List<TreeViewItem>(); 

     for (int index = 0; index < treeViewItem.Items.Count; index++) 
     { 
      TreeViewItem item = (TreeViewItem)treeViewItem.ItemContainerGenerator.ContainerFromIndex(index); 
      if (item != null) 
      { 
       returnItems.Add(item); 
       if (includeCollapsedItems || item.IsExpanded) 
       { 
        returnItems.AddRange(GetTreeViewItemItems(item, includeCollapsedItems)); 
       } 
      } 
     } 

     return returnItems; 
    } 

    #endregion 
} 
} 

Answer 4

tengo una variación en la aplicación SoMoS que usa una propiedad adjunta declarada en una derivación del control TreeView base para rastrear el estado de selección de TreeViewItems. Esto mantiene el seguimiento de selección en el elemento TreeViewItem en sí mismo y fuera del objeto modelo presentado por la vista en árbol.

Esta es la nueva derivación de la clase TreeView.

using System.Linq; 
using System.Windows; 
using System.Windows.Input; 
using System.Windows.Media; 
using System.Windows.Shapes; 
using System.Windows.Controls; 
using System.Collections; 
using System.Collections.Generic; 

namespace MultiSelectTreeViewDemo 
{ 
    public sealed class MultiSelectTreeView : TreeView 
    { 
     #region Fields 

     // Used in shift selections 
     private TreeViewItem _lastItemSelected; 

     #endregion Fields 
     #region Dependency Properties 

     public static readonly DependencyProperty IsItemSelectedProperty = 
      DependencyProperty.RegisterAttached("IsItemSelected", typeof(bool), typeof(MultiSelectTreeView)); 

     public static void SetIsItemSelected(UIElement element, bool value) 
     { 
      element.SetValue(IsItemSelectedProperty, value); 
     } 
     public static bool GetIsItemSelected(UIElement element) 
     { 
      return (bool)element.GetValue(IsItemSelectedProperty); 
     } 

     #endregion Dependency Properties 
     #region Properties 

     private static bool IsCtrlPressed 
     { 
      get { return Keyboard.IsKeyDown(Key.LeftCtrl) || Keyboard.IsKeyDown(Key.RightCtrl); } 
     } 
     private static bool IsShiftPressed 
     { 
      get { return Keyboard.IsKeyDown(Key.LeftShift) || Keyboard.IsKeyDown(Key.RightShift); } 
     } 

     public IList SelectedItems 
     { 
      get 
      { 
       var selectedTreeViewItems = GetTreeViewItems(this, true).Where(GetIsItemSelected); 
       var selectedModelItems = selectedTreeViewItems.Select(treeViewItem => treeViewItem.Header); 

       return selectedModelItems.ToList(); 
      } 
     } 

     #endregion Properties 
     #region Event Handlers 

     protected override void OnPreviewMouseDown(MouseButtonEventArgs e) 
     { 
      base.OnPreviewMouseDown(e); 

      // If clicking on a tree branch expander... 
      if (e.OriginalSource is Shape || e.OriginalSource is Grid || e.OriginalSource is Border) 
       return; 

      var item = GetTreeViewItemClicked((FrameworkElement)e.OriginalSource); 
      if (item != null) SelectedItemChangedInternal(item); 
     } 

     #endregion Event Handlers 
     #region Utility Methods 

     private void SelectedItemChangedInternal(TreeViewItem tvItem) 
     { 
      // Clear all previous selected item states if ctrl is NOT being held down 
      if (!IsCtrlPressed) 
      { 
       var items = GetTreeViewItems(this, true); 
       foreach (var treeViewItem in items) 
        SetIsItemSelected(treeViewItem, false); 
      } 

      // Is this an item range selection? 
      if (IsShiftPressed && _lastItemSelected != null) 
      { 
       var items = GetTreeViewItemRange(_lastItemSelected, tvItem); 
       if (items.Count > 0) 
       { 
        foreach (var treeViewItem in items) 
         SetIsItemSelected(treeViewItem, true); 

        _lastItemSelected = items.Last(); 
       } 
      } 
      // Otherwise, individual selection 
      else 
      { 
       SetIsItemSelected(tvItem, true); 
       _lastItemSelected = tvItem; 
      } 
     } 
     private static TreeViewItem GetTreeViewItemClicked(DependencyObject sender) 
     { 
      while (sender != null && !(sender is TreeViewItem)) 
       sender = VisualTreeHelper.GetParent(sender); 
      return sender as TreeViewItem; 
     } 
     private static List<TreeViewItem> GetTreeViewItems(ItemsControl parentItem, bool includeCollapsedItems, List<TreeViewItem> itemList = null) 
     { 
      if (itemList == null) 
       itemList = new List<TreeViewItem>(); 

      for (var index = 0; index < parentItem.Items.Count; index++) 
      { 
       var tvItem = parentItem.ItemContainerGenerator.ContainerFromIndex(index) as TreeViewItem; 
       if (tvItem == null) continue; 

       itemList.Add(tvItem); 
       if (includeCollapsedItems || tvItem.IsExpanded) 
        GetTreeViewItems(tvItem, includeCollapsedItems, itemList); 
      } 
      return itemList; 
     } 
     private List<TreeViewItem> GetTreeViewItemRange(TreeViewItem start, TreeViewItem end) 
     { 
      var items = GetTreeViewItems(this, false); 

      var startIndex = items.IndexOf(start); 
      var endIndex = items.IndexOf(end); 
      var rangeStart = startIndex > endIndex || startIndex == -1 ? endIndex : startIndex; 
      var rangeCount = startIndex > endIndex ? startIndex - endIndex + 1 : endIndex - startIndex + 1; 

      if (startIndex == -1 && endIndex == -1) 
       rangeCount = 0; 

      else if (startIndex == -1 || endIndex == -1) 
       rangeCount = 1; 

      return rangeCount > 0 ? items.GetRange(rangeStart, rangeCount) : new List<TreeViewItem>(); 
     } 

     #endregion Utility Methods 
    } 
} 

Y aquí está el XAML.Tenga en cuenta que la parte saliente es la sustitución de los dos activadores que utilizan la propiedad singular 'IsSelected' con la nueva propiedad adjunta 'IsItemSelected' en MultiSelectTreeViewItemStyle para lograr el estado visual.

También tenga en cuenta que no estoy agregando el nuevo control TreeView en un UserControl.

<Window 
    x:Class="MultiSelectTreeViewDemo.MainWindow" 
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" 
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" 
    xmlns:local="clr-namespace:MultiSelectTreeViewDemo" 
    Title="MultiSelect TreeView Demo" Height="350" Width="525"> 

    <Window.Resources> 
     <local:DemoViewModel x:Key="ViewModel"/> 
     <Style x:Key="TreeViewItemFocusVisual"> 
      <Setter Property="Control.Template"> 
       <Setter.Value> 
        <ControlTemplate> 
         <Rectangle/> 
        </ControlTemplate> 
       </Setter.Value> 
      </Setter> 
     </Style> 
     <SolidColorBrush x:Key="TreeViewItem.TreeArrow.Static.Checked.Fill" Color="#FF595959"/> 
     <SolidColorBrush x:Key="TreeViewItem.TreeArrow.Static.Checked.Stroke" Color="#FF262626"/> 
     <SolidColorBrush x:Key="TreeViewItem.TreeArrow.MouseOver.Stroke" Color="#FF1BBBFA"/> 
     <SolidColorBrush x:Key="TreeViewItem.TreeArrow.MouseOver.Fill" Color="Transparent"/> 
     <SolidColorBrush x:Key="TreeViewItem.TreeArrow.MouseOver.Checked.Stroke" Color="#FF262626"/> 
     <SolidColorBrush x:Key="TreeViewItem.TreeArrow.MouseOver.Checked.Fill" Color="#FF595959"/> 
     <PathGeometry x:Key="TreeArrow" Figures="M0,0 L0,6 L6,0 z"/> 
     <SolidColorBrush x:Key="TreeViewItem.TreeArrow.Static.Fill" Color="Transparent"/> 
     <SolidColorBrush x:Key="TreeViewItem.TreeArrow.Static.Stroke" Color="#FF989898"/> 
     <Style x:Key="ExpandCollapseToggleStyle" TargetType="{x:Type ToggleButton}"> 
      <Setter Property="Focusable" Value="False"/> 
      <Setter Property="Width" Value="16"/> 
      <Setter Property="Height" Value="16"/> 
      <Setter Property="Template"> 
       <Setter.Value> 
        <ControlTemplate TargetType="{x:Type ToggleButton}"> 
         <Border Background="Transparent" Height="16" Padding="5,5,5,5" Width="16"> 
          <Path x:Name="ExpandPath" Data="{StaticResource TreeArrow}" Fill="{StaticResource TreeViewItem.TreeArrow.Static.Fill}" Stroke="{StaticResource TreeViewItem.TreeArrow.Static.Stroke}"> 
           <Path.RenderTransform> 
            <RotateTransform Angle="135" CenterY="3" CenterX="3"/> 
           </Path.RenderTransform> 
          </Path> 
         </Border> 
         <ControlTemplate.Triggers> 
          <Trigger Property="IsChecked" Value="True"> 
           <Setter Property="RenderTransform" TargetName="ExpandPath"> 
            <Setter.Value> 
             <RotateTransform Angle="180" CenterY="3" CenterX="3"/> 
            </Setter.Value> 
           </Setter> 
           <Setter Property="Fill" TargetName="ExpandPath" Value="{StaticResource TreeViewItem.TreeArrow.Static.Checked.Fill}"/> 
           <Setter Property="Stroke" TargetName="ExpandPath" Value="{StaticResource TreeViewItem.TreeArrow.Static.Checked.Stroke}"/> 
          </Trigger> 
          <Trigger Property="IsMouseOver" Value="True"> 
           <Setter Property="Stroke" TargetName="ExpandPath" Value="{StaticResource TreeViewItem.TreeArrow.MouseOver.Stroke}"/> 
           <Setter Property="Fill" TargetName="ExpandPath" Value="{StaticResource TreeViewItem.TreeArrow.MouseOver.Fill}"/> 
          </Trigger> 
          <MultiTrigger> 
           <MultiTrigger.Conditions> 
            <Condition Property="IsMouseOver" Value="True"/> 
            <Condition Property="IsChecked" Value="True"/> 
           </MultiTrigger.Conditions> 
           <Setter Property="Stroke" TargetName="ExpandPath" Value="{StaticResource TreeViewItem.TreeArrow.MouseOver.Checked.Stroke}"/> 
           <Setter Property="Fill" TargetName="ExpandPath" Value="{StaticResource TreeViewItem.TreeArrow.MouseOver.Checked.Fill}"/> 
          </MultiTrigger> 
         </ControlTemplate.Triggers> 
        </ControlTemplate> 
       </Setter.Value> 
      </Setter> 
     </Style> 
     <Style x:Key="MultiSelectTreeViewItemStyle" TargetType="{x:Type TreeViewItem}"> 
      <Setter Property="Background" Value="Transparent"/> 
      <Setter Property="HorizontalContentAlignment" Value="{Binding HorizontalContentAlignment, RelativeSource={RelativeSource AncestorType={x:Type ItemsControl}}}"/> 
      <Setter Property="VerticalContentAlignment" Value="{Binding VerticalContentAlignment, RelativeSource={RelativeSource AncestorType={x:Type ItemsControl}}}"/> 
      <Setter Property="Padding" Value="1,0,0,0"/> 
      <Setter Property="Foreground" Value="{DynamicResource {x:Static SystemColors.ControlTextBrushKey}}"/> 
      <Setter Property="FocusVisualStyle" Value="{StaticResource TreeViewItemFocusVisual}"/> 
      <Setter Property="Template"> 
       <Setter.Value> 
        <ControlTemplate TargetType="{x:Type TreeViewItem}"> 
         <Grid> 
          <Grid.ColumnDefinitions> 
           <ColumnDefinition MinWidth="19" Width="Auto"/> 
           <ColumnDefinition Width="Auto"/> 
           <ColumnDefinition Width="*"/> 
          </Grid.ColumnDefinitions> 
          <Grid.RowDefinitions> 
           <RowDefinition Height="Auto"/> 
           <RowDefinition/> 
          </Grid.RowDefinitions> 
          <ToggleButton 
           x:Name="Expander" 
           ClickMode="Press" 
           IsChecked="{Binding IsExpanded, RelativeSource={RelativeSource TemplatedParent}}" 
           Style="{StaticResource ExpandCollapseToggleStyle}"/> 
          <Border 
           x:Name="Bd" 
           BorderBrush="{TemplateBinding BorderBrush}" 
           BorderThickness="{TemplateBinding BorderThickness}" 
           Background="{TemplateBinding Background}" 
           Grid.Column="1" 
           Padding="{TemplateBinding Padding}" 
           SnapsToDevicePixels="true"> 
           <ContentPresenter 
            x:Name="PART_Header" 
            ContentSource="Header" 
            HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}" 
            SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}"/> 
          </Border> 
          <ItemsPresenter 
           x:Name="ItemsHost" 
           Grid.ColumnSpan="2" 
           Grid.Column="1" 
           Grid.Row="1"/> 
         </Grid> 
         <ControlTemplate.Triggers> 
          <Trigger Property="IsExpanded" Value="false"> 
           <Setter Property="Visibility" TargetName="ItemsHost" Value="Collapsed"/> 
          </Trigger> 
          <Trigger Property="HasItems" Value="false"> 
           <Setter Property="Visibility" TargetName="Expander" Value="Hidden"/> 
          </Trigger> 
          <!--Trigger Property="IsSelected" Value="true"--> 
          <Trigger Property="local:MultiSelectTreeView.IsItemSelected" Value="true"> 
           <Setter Property="Background" TargetName="Bd" Value="{DynamicResource {x:Static SystemColors.HighlightBrushKey}}"/> 
           <Setter Property="Foreground" Value="{DynamicResource {x:Static SystemColors.HighlightTextBrushKey}}"/> 
          </Trigger> 
          <MultiTrigger> 
           <MultiTrigger.Conditions> 
            <!--Condition Property="IsSelected" Value="true"/--> 
            <Condition Property="local:MultiSelectTreeView.IsItemSelected" Value="true"/> 
            <Condition Property="IsSelectionActive" Value="false"/> 
           </MultiTrigger.Conditions> 
           <Setter Property="Background" TargetName="Bd" Value="{DynamicResource {x:Static SystemColors.InactiveSelectionHighlightBrushKey}}"/> 
           <Setter Property="Foreground" Value="{DynamicResource {x:Static SystemColors.InactiveSelectionHighlightTextBrushKey}}"/> 
          </MultiTrigger> 
          <Trigger Property="IsEnabled" Value="false"> 
           <Setter Property="Foreground" Value="{DynamicResource {x:Static SystemColors.GrayTextBrushKey}}"/> 
          </Trigger> 
         </ControlTemplate.Triggers> 
        </ControlTemplate> 
       </Setter.Value> 
      </Setter> 
      <Style.Triggers> 
       <Trigger Property="VirtualizingPanel.IsVirtualizing" Value="true"> 
        <Setter Property="ItemsPanel"> 
         <Setter.Value> 
          <ItemsPanelTemplate> 
           <VirtualizingStackPanel/> 
          </ItemsPanelTemplate> 
         </Setter.Value> 
        </Setter> 
       </Trigger> 
      </Style.Triggers> 
     </Style> 
    </Window.Resources> 

    <Grid 
     Background="WhiteSmoke" 
     DataContext="{DynamicResource ViewModel}"> 
     <Grid.RowDefinitions> 
      <RowDefinition/> 
      <RowDefinition Height="Auto"/> 
     </Grid.RowDefinitions> 
     <local:MultiSelectTreeView 
      x:Name="multiSelectTreeView" 
      ItemContainerStyle="{StaticResource MultiSelectTreeViewItemStyle}" 
      ItemsSource="{Binding FoodGroups}"> 
      <local:MultiSelectTreeView.ItemTemplate> 
       <HierarchicalDataTemplate ItemsSource="{Binding Children}"> 
        <Grid> 
         <TextBlock FontSize="14" Text="{Binding Name}"/> 
        </Grid> 
       </HierarchicalDataTemplate> 
      </local:MultiSelectTreeView.ItemTemplate> 
     </local:MultiSelectTreeView> 
     <Button 
      Grid.Row="1" 
      Margin="0,10" 
      Padding="20,2" 
      HorizontalAlignment="Center" 
      Content="Get Selections" 
      Click="GetSelectionsButton_OnClick"/> 
    </Grid> 
</Window> 

Y aquí hay un cursi modelo de vista para manejarlo (con fines de demostración).

using System.Collections.ObjectModel; 

namespace MultiSelectTreeViewDemo 
{ 
    public sealed class DemoViewModel 
    { 
     public ObservableCollection<FoodItem> FoodGroups { get; set; } 

     public DemoViewModel() 
     { 
      var redMeat = new FoodItem { Name = "Reds" }; 
      redMeat.Add(new FoodItem { Name = "Beef" }); 
      redMeat.Add(new FoodItem { Name = "Buffalo" }); 
      redMeat.Add(new FoodItem { Name = "Lamb" }); 

      var whiteMeat = new FoodItem { Name = "Whites" }; 
      whiteMeat.Add(new FoodItem { Name = "Chicken" }); 
      whiteMeat.Add(new FoodItem { Name = "Duck" }); 
      whiteMeat.Add(new FoodItem { Name = "Pork" }); 
      var meats = new FoodItem { Name = "Meats", Children = { redMeat, whiteMeat } }; 

      var veggies = new FoodItem { Name = "Vegetables" }; 
      veggies.Add(new FoodItem { Name = "Potato" }); 
      veggies.Add(new FoodItem { Name = "Corn" }); 
      veggies.Add(new FoodItem { Name = "Spinach" }); 

      var fruits = new FoodItem { Name = "Fruits" }; 
      fruits.Add(new FoodItem { Name = "Apple" }); 
      fruits.Add(new FoodItem { Name = "Orange" }); 
      fruits.Add(new FoodItem { Name = "Pear" }); 

      FoodGroups = new ObservableCollection<FoodItem> { meats, veggies, fruits }; 
     } 
    } 
    public sealed class FoodItem 
    { 
     public string Name { get; set; } 
     public ObservableCollection<FoodItem> Children { get; set; } 

     public FoodItem() 
     { 
      Children = new ObservableCollection<FoodItem>(); 
     } 
     public void Add(FoodItem item) 
     { 
      Children.Add(item); 
     } 
    } 
} 

Y aquí está el botón de clic-manejador en la MainWindow de código subyacente que muestra las selecciones en un cuadro de mensaje.

private void GetSelectionsButton_OnClick(object sender, RoutedEventArgs e) 
    { 
     var selectedMesg = ""; 
     var selectedItems = multiSelectTreeView.SelectedItems; 

     if (selectedItems.Count > 0) 
     { 
      selectedMesg = selectedItems.Cast<FoodItem>() 
       .Where(modelItem => modelItem != null) 
       .Aggregate(selectedMesg, (current, modelItem) => current + modelItem.Name + Environment.NewLine); 
     } 
     else 
      selectedMesg = "No selected items!"; 

     MessageBox.Show(selectedMesg, "MultiSelect TreeView Demo", MessageBoxButton.OK); 
    } 

Espero que esto ayude.