如何以编程方式选择 WPF TreeView 中的项目？

Question

如何以编程方式选择 WPF TreeView 中的项目？ ItemsControl 模型似乎可以阻止它。

Answer 1

对于那些仍在寻找此问题的正确解决方案的人，请参阅以下内容。我在 DaWanderer 的代码项目文章“WPF TreeView Selection”http://www.codeproject.com/KB/WPF/TreeView_SelectionWPF.aspx 的 cmets 中找到了这个。 它由 Kenrae 于 2008 年 11 月 25 日发布。这对我来说非常有用。谢谢肯雷！

这是他的帖子：

让您自己的数据对象拥有 IsSelected 属性（我也推荐 IsExpanded 属性），而不是遍历树。使用 TreeView 上的 ItemContainerStyle 属性定义树的 TreeViewItems 的样式，该属性将 TreeViewItem 中的这些属性绑定到您的数据对象。像这样的：

<Style x:Key="LibraryTreeViewItemStyle"
               TargetType="{x:Type TreeViewItem}">
            <Setter Property="IsExpanded"
                        Value="{Binding IsExpanded, Mode=TwoWay}" />
            <Setter Property="IsSelected"
                        Value="{Binding IsSelected, Mode=TwoWay}" />
            <Setter Property="FontWeight"
                        Value="Normal" />
            <Style.Triggers>
                  <Trigger Property="IsSelected"
                              Value="True">
                        <Setter Property="FontWeight"
                                    Value="Bold" />
                  </Trigger>
            </Style.Triggers>
      </Style>

<TreeView ItemsSource="{Binding Path=YourCollection}"
               ItemContainerStyle="{StaticResource LibraryTreeViewItemStyle}"
               ItemTemplate={StaticResource YourHierarchicalDataTemplate}/>

Answer 2

出于某种奇怪的原因，这真的很痛苦，您必须使用 ContainerFromItem 来获取容器，然后调用 select 方法。

//  selectedItemObject is not a TreeViewItem, but an item from the collection that 
//  populated the TreeView.

var tvi = treeView.ItemContainerGenerator.ContainerFromItem(selectedItemObject) 
          as TreeViewItem;

if (tvi != null)
{
    tvi.IsSelected = true;
}

曾经有一篇关于如何做到这一点的博客文章here，但现在链接已失效。

Answer 3

您需要获取TreeViewItem，然后将IsSelected 设置为true。

Answer 4

我已成功使用此代码：

public static TreeViewItem FindTviFromObjectRecursive(ItemsControl ic, object o) {
  //Search for the object model in first level children (recursively)
  TreeViewItem tvi = ic.ItemContainerGenerator.ContainerFromItem(o) as TreeViewItem;
  if (tvi != null) return tvi;
  //Loop through user object models
  foreach (object i in ic.Items) {
    //Get the TreeViewItem associated with the iterated object model
    TreeViewItem tvi2 = ic.ItemContainerGenerator.ContainerFromItem(i) as TreeViewItem;
    tvi = FindTviFromObjectRecursive(tvi2, o);
    if (tvi != null) return tvi;
  }
  return null;
}

用法：

var tvi = FindTviFromObjectRecursive(TheTreeView, TheModel);
if (tvi != null) tvi.IsSelected = true;

Answer 5

这并不像看起来那么简单，Steven 提供的链接在 2008 年发布了一个解决方案，该解决方案可能仍然有效，但无法处理虚拟化 TreeViews。此外，该文章的 cmets 中还提到了许多其他问题。没有冒犯，但我也遇到了同样的问题，找不到完美的解决方案。以下是一些对我有很大帮助的文章/帖子的链接-

如何在 TreeView 中展开项目？ – 第三部分： http://bea.stollnitz.com/blog/?p=59

以编程方式在 TreeView 中选择项目： http://blog.quantumbitdesigns.com/2008/07/22/programmatically-selecting-an-item-in-a-treeview/#respond

TreeView、TreeViewItem 和 IsSelected： http://social.msdn.microsoft.com/Forums/en-US/wpf/thread/7e368b93-f509-4cd6-88e7-561e8d3246ae/

Answer 6

我写了一个扩展方法：

using System.Windows.Controls;

namespace Extensions
{
    public static class TreeViewEx
    {
        /// <summary>
        /// Select specified item in a TreeView
        /// </summary>
        public static void SelectItem(this TreeView treeView, object item)
        {
            var tvItem = treeView.ItemContainerGenerator.ContainerFromItem(item) as TreeViewItem;
            if (tvItem != null)
            {
                tvItem.IsSelected = true;
            }
        }
    }
}

我可以这样使用：

if (_items.Count > 0)
    _treeView.SelectItem(_items[0]);

Answer 7

如果您想选择位于孩子的孩子的项目，您可以使用递归来做到这一点。

public bool Select(TreeViewItem item, object select) // recursive function to set item selection in treeview
{
    if (item == null)
        return false;
    TreeViewItem child = item.ItemContainerGenerator.ContainerFromItem(select) as TreeViewItem;
    if (child != null)
    {
        child.IsSelected = true;
        return true;
    }
    foreach (object c in item.Items)
    {
        bool result = Select(item.ItemContainerGenerator.ContainerFromItem(c) as TreeViewItem, select);
        if (result == true)
            return true;
    }
    return false;
}

Answer 8

你可以通过后面的代码来做到这一点

if (TreeView1.Items.Count > 0)
        (TreeView1.Items[0] as TreeViewItem).IsSelected = true;

Answer 9

试试这个

    /// <summary>
    /// Selects the tree view item.
    /// </summary>
    /// <param name="Collection">The collection.</param>
    /// <param name="Value">The value.</param>
    /// <returns></returns>
    private TreeViewItem SelectTreeViewItem(ItemCollection Collection, String Value)
    {
        if (Collection == null) return null;
        foreach(TreeViewItem Item in Collection)
        {
            /// Find in current
            if (Item.Header.Equals(Value))
            {
                Item.IsSelected = true;
                return Item;
            }
            /// Find in Childs
            if (Item.Items != null)
            {
                TreeViewItem childItem = this.SelectTreeViewItem(Item.Items, Value);
                if (childItem != null)
                {
                    Item.IsExpanded = true;
                    return childItem;
                }
            }
        }
        return null;
    }

参考：http://amastaneh.blogspot.com/2011/06/wpf-selectedvalue-for-treeview.html

Answer 10

只是想我会加入我所采用的解决方案，以防万一这可以帮助任何人。请注意，执行此操作的最佳方法是根据 kuninl 的回答使用像“IsSelected”这样的绑定属性，但在我的情况下，它是一个不遵循 MVVM 的遗留应用程序，所以我最终得到了以下结果。

private void ChangeSessionSelection()
{
    foreach (SessionContainer item in this.treeActiveSessions.Items)
    {
        var treeviewItem = this.treeActiveSessions.ItemContainerGenerator.ContainerFromItem(item) as TreeViewItem;

        if (item.Session == this.selectedSession.Session)
        {
            treeviewItem.IsSelected = true;
            treeviewItem.IsExpanded = true;
        }
        else
        {
            treeviewItem.IsSelected = false;
            treeviewItem.IsExpanded = false;
        }
    }            
}

它的作用是在 UI 中选择并展开树视图项，它代表后面代码中选定的数据项。这样做的目的是当用户在同一窗口中的项目控件中更改选择时，在树视图中更改选择。

Answer 11

我创建了一个方法VisualTreeExt.GetDescendants<T>，它返回与指定类型匹配的可枚举元素集合：

public static class VisualTreeExt
{
  public static IEnumerable<T> GetDescendants<T>(DependencyObject parent) where T : DependencyObject
  {
    var count = VisualTreeHelper.GetChildrenCount(parent);
    for (var i = 0; i < count; ++i)
    {
       // Obtain the child
       var child = VisualTreeHelper.GetChild(parent, i);
       if (child is T)
         yield return (T)child;

       // Return all the descendant children
       foreach (var subItem in GetDescendants<T>(child))
         yield return subItem;
    }
  }
}

当您请求 VisualTreeHelperExt.GetDescendants<TreeViewItem>(MyAmazingTreeView) 时，您将获得所有 TreeViewItem 子代。您可以使用以下代码选择特定值：

var treeViewItem = VisualTreeExt.GetDescendants<TreeViewItem>(MyTreeView).FirstOrDefault(tvi => tvi.DataContext == newValue);
if (treeViewItem != null)
  treeViewItem.IsSelected = true;

这是一个有点肮脏的解决方案（可能不是最有效的），如果您使用虚拟化 TreeView，它将无法工作，因为它取决于实际视觉元素的存在。但它适用于我的情况......

Answer 12

建议的答案不起作用。 @fandisusanto 的答案可能确实有效，但它可以变得更简单。这是我能想到的最简单的答案：

    private static void DeselectTreeViewItem(IEnumerable<TreeViewItem> treeViewItems)
    {
        foreach (var treeViewItem in treeViewItems)
        {
            if (treeViewItem.IsSelected)
            {
                treeViewItem.IsSelected = false;
                return;
            }

            DeselectTreeViewItem(treeViewItem.Items.Cast<TreeViewItem>());
        }
    }

用法：

    private void ClearSelectedItem()
    {
        if (AssetTreeView.SelectedItem != null)
        {
            DeselectTreeViewItem(AssetTreeView.Items.Cast<TreeViewItem>());
        }
    }

Answer 13

这是我的解决方案。其他人以各种方式对我来说失败了。您需要从上到下遍历树，在每个级别查找树项，沿途扩展和更新布局。

此函数获取一个节点堆栈，其中第一个出堆栈的节点是最顶部的节点，堆栈上的每个后续节点都是前一个父节点的子节点。第二个参数是 TreeView。

找到每个项目后，展开该项目，并返回最后一个项目，调用者可以在其中选择它。

    TreeViewItem FindTreeViewItem( Stack<object> nodeStack, TreeView treeView )
    {
        ItemsControl itemsControl = treeView;

        while (nodeStack.Count > 0) {
            object node = nodeStack.Pop();
            bool found = false;

            foreach (object item in itemsControl.Items) {
                if (item == node) {
                    found = true;

                    if (itemsControl.ItemContainerGenerator.ContainerFromItem( item ) is TreeViewItem treeViewItem) {
                        if (nodeStack.Count == 0) {
                            return treeViewItem;
                        }

                        itemsControl = treeViewItem;
                        treeViewItem.IsExpanded = true;
                        treeViewItem.UpdateLayout();
                        break;
                    }
                }
            }

            if (!found) {
                return null;
            }
        }

        return null;
    }

如何调用它的示例：

    // Build nodeStack here from your data

    TreeViewItem treeViewItem = FindTreeViewItem( nodeStack, treeView );

    if (treeViewItem != null) {
        treeViewItem.IsSelected = true;
        treeViewItem.BringIntoView();
    }

Answer 14

我为此编写了一个 Helper 类，它支持 MVVM 和延迟加载项。

public class TreeViewHelper<TModel>
{
    public TreeViewHelper(TreeView treeView, Func<TModel, TModel> getParent, Func<TModel, IList<TModel>> getSubItems)
    {
        TreeView = treeView;
        GetParent = getParent;
        GetSubItems = getSubItems;
    }

    public TreeView TreeView { get; }
    public Func<TModel, TModel> GetParent { get; }
    public Func<TModel, IList<TModel>> GetSubItems { get; }

    public void SelectItemWhileLoaded(TModel node, IList<TModel> rootNodes)
    {
        if (TreeView.IsLoaded)
        {
            SelectItem(node, rootNodes);
        }
        else
        {
            TreeView.Loaded += TreeView_Loaded;
            void TreeView_Loaded(object sender, System.Windows.RoutedEventArgs e)
            {
                TreeView.Loaded -= TreeView_Loaded;
                SelectItem(node, rootNodes);
            }
        }
    }


    public void SelectItem(TModel node, IList<TModel> rootNodes)
    {
        Stack<TModel> nodes = new Stack<TModel>();
        //push into stack
        while (!rootNodes.Contains(node))
        {
            nodes.Push(node);
            node = GetParent(node);
        }
        TreeViewItem treeViewItem = TreeView.ItemContainerGenerator
            .ContainerFromItem(node) as TreeViewItem;
        if (nodes.Count == 0)
        {
            //Top level
            treeViewItem.IsSelected = true;
            treeViewItem.BringIntoView();
            return;
        }
        Expanded(true);
        void Expanded(bool top)
        {
            if (!top)
            {
                treeViewItem = treeViewItem.ItemContainerGenerator
                    .ContainerFromItem(node) as TreeViewItem;
                if (nodes.Count == 0)
                {
                    treeViewItem.IsSelected = true;
                    treeViewItem.BringIntoView();
                    return;
                }
            }
            node = nodes.Pop();
            treeViewItem.IsExpanded = true;
            if (treeViewItem.ItemContainerGenerator.Status == GeneratorStatus.ContainersGenerated)
            {
                Expanded(true);
            }
            else
            {
                //Lazy
                treeViewItem.ItemContainerGenerator.StatusChanged += ItemContainerGenerator_StatusChanged;
            }
        }
        void ItemContainerGenerator_StatusChanged(object sender, EventArgs e)
        {
            if (treeViewItem.ItemContainerGenerator.Status == GeneratorStatus.ContainersGenerated)
            {
                treeViewItem.ItemContainerGenerator.StatusChanged -= ItemContainerGenerator_StatusChanged;
                Expanded(false);
            }
        }
    }
}

Answer 15

是的..我知道这个问题已经过去很多年了，但是..仍然没有快速解决这个问题..所以：

以下将执行 OP 要求的操作。

我所做的基本上是阅读此页面中的所有答案并点击所有相关链接以创建一个一劳永逸的解决方案来解决这个恼人的问题。

好处：

• 它也支持虚拟化 TreeView。
• 它使用行为技术，因此 XAML 非常简单。
• 添加依赖属性以允许绑定到选定的 TreeView 项。

这部分是你唯一需要复制的代码，其他部分只是为了帮助完成一个例子。

public static class TreeViewSelectedItemExBehavior
{
    private static List<TreeView> isRegisteredToSelectionChanged = new List<TreeView>();

    public static readonly DependencyProperty SelectedItemExProperty =
        DependencyProperty.RegisterAttached("SelectedItemEx",
            typeof(object),
            typeof(TreeViewSelectedItemExBehavior),
            new FrameworkPropertyMetadata(new object(), FrameworkPropertyMetadataOptions.BindsTwoWayByDefault, OnSelectedItemExChanged, null));

    #region SelectedItemEx

    public static object GetSelectedItemEx(TreeView target)
    {
        return target.GetValue(SelectedItemExProperty);
    }

    public static void SetSelectedItemEx(TreeView target, object value)
    {
        target.SetValue(SelectedItemExProperty, value);
        var treeViewItemToSelect = GetTreeViewItem(target, value);
        if (treeViewItemToSelect == null)
        {
            if (target.SelectedItem == null)
                return;
            var treeViewItemToUnSelect = GetTreeViewItem(target, target.SelectedItem);
            treeViewItemToUnSelect.IsSelected = false;
        }
        else
            treeViewItemToSelect.IsSelected = true;
    }

    public static void OnSelectedItemExChanged(DependencyObject depObj, DependencyPropertyChangedEventArgs e)
    {
        var treeView = depObj as TreeView;
        if (treeView == null)
            return;
        if (!isRegisteredToSelectionChanged.Contains(treeView))
        {
            treeView.SelectedItemChanged += TreeView_SelectedItemChanged;
            isRegisteredToSelectionChanged.Add(treeView);
        }
    }
    
    #endregion

    private static void TreeView_SelectedItemChanged(object sender, RoutedPropertyChangedEventArgs<object> e)
    {
        var treeView = (TreeView)sender;
        SetSelectedItemEx(treeView, e.NewValue);
    }

    #region Helper Structures & Methods

    public class MyVirtualizingStackPanel : VirtualizingStackPanel
    {
        /// <summary>
        /// Publically expose BringIndexIntoView.
        /// </summary>
        public void BringIntoView(int index)
        {
            BringIndexIntoView(index);
        }
    }

    /// <summary>Recursively search for an item in this subtree.</summary>
    /// <param name="container">The parent ItemsControl. This can be a TreeView or a TreeViewItem.</param>
    /// <param name="item">The item to search for.</param>
    /// <returns>The TreeViewItem that contains the specified item.</returns>
    private static TreeViewItem GetTreeViewItem(ItemsControl container, object item)
    {
        if (container != null)
        {
            if (container.DataContext == item)
            {
                return container as TreeViewItem;
            }

            // Expand the current container
            if (container is TreeViewItem && !((TreeViewItem)container).IsExpanded)
            {
                container.SetValue(TreeViewItem.IsExpandedProperty, true);
            }

            // Try to generate the ItemsPresenter and the ItemsPanel.
            // by calling ApplyTemplate.  Note that in the 
            // virtualizing case even if the item is marked 
            // expanded we still need to do this step in order to 
            // regenerate the visuals because they may have been virtualized away.

            container.ApplyTemplate();
            ItemsPresenter itemsPresenter =
                (ItemsPresenter)container.Template.FindName("ItemsHost", container);
            if (itemsPresenter != null)
            {
                itemsPresenter.ApplyTemplate();
            }
            else
            {
                // The Tree template has not named the ItemsPresenter, 
                // so walk the descendents and find the child.
                itemsPresenter = FindVisualChild<ItemsPresenter>(container);
                if (itemsPresenter == null)
                {
                    container.UpdateLayout();

                    itemsPresenter = FindVisualChild<ItemsPresenter>(container);
                }
            }

            Panel itemsHostPanel = (Panel)VisualTreeHelper.GetChild(itemsPresenter, 0);


            // Ensure that the generator for this panel has been created.
            UIElementCollection children = itemsHostPanel.Children;

            MyVirtualizingStackPanel virtualizingPanel =
                itemsHostPanel as MyVirtualizingStackPanel;

            for (int i = 0, count = container.Items.Count; i < count; i++)
            {
                TreeViewItem subContainer;
                if (virtualizingPanel != null)
                {
                    // Bring the item into view so 
                    // that the container will be generated.
                    virtualizingPanel.BringIntoView(i);

                    subContainer =
                        (TreeViewItem)container.ItemContainerGenerator.
                        ContainerFromIndex(i);
                }
                else
                {
                    subContainer =
                        (TreeViewItem)container.ItemContainerGenerator.
                        ContainerFromIndex(i);

                    // Bring the item into view to maintain the 
                    // same behavior as with a virtualizing panel.
                    subContainer.BringIntoView();
                }

                if (subContainer != null)
                {
                    // Search the next level for the object.
                    TreeViewItem resultContainer = GetTreeViewItem(subContainer, item);
                    if (resultContainer != null)
                    {
                        return resultContainer;
                    }
                    else
                    {
                        // The object is not under this TreeViewItem
                        // so collapse it.
                        subContainer.IsExpanded = false;
                    }
                }
            }
        }

        return null;
    }

    /// <summary>Search for an element of a certain type in the visual tree.</summary>
    /// <typeparam name="T">The type of element to find.</typeparam>
    /// <param name="visual">The parent element.</param>
    /// <returns></returns>
    private static T FindVisualChild<T>(Visual visual) where T : Visual
    {
        for (int i = 0; i < VisualTreeHelper.GetChildrenCount(visual); i++)
        {
            Visual child = (Visual)VisualTreeHelper.GetChild(visual, i);
            if (child != null)
            {
                T correctlyTyped = child as T;
                if (correctlyTyped != null)
                {
                    return correctlyTyped;
                }

                T descendent = FindVisualChild<T>(child);
                if (descendent != null)
                {
                    return descendent;
                }
            }
        }
        return null;
    }
    
    #endregion
}

这是 TreeView 行在 XAML 中的外观示例：

<TreeView x:Name="trvwSs"
    Grid.Column="2" Grid.Row="1" Margin="4" ItemsSource="{Binding ItemsTreeViewSs}"
    behaviors:TreeViewSelectedItemExBehavior.SelectedItemEx="{Binding SelectedItemTreeViewSs}" />

唯一需要担心的是确保要绑定到 SelectedItemEx 的视图模型属性不为空。但这不是特例。只是提到它以防人们感到困惑。

public class VmMainContainer : INotifyPropertyChanged
{
    private object selectedItemTreeViewSs = new object();
    private ObservableCollection<object> selectedItemsTreeViewSs = new ObservableCollection<object>();
    private ObservableCollection<VmItem> itemsTreeViewSs = new ObservableCollection<VmItem>();

    public object SelectedItemTreeViewSs
    {
        get
        {
            return selectedItemTreeViewSs;
        }
        set
        {
            selectedItemTreeViewSs = value;
            PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(nameof(SelectedItemTreeViewSs)));
        }
    }

    public ObservableCollection<object> SelectedItemsTreeViewSs
    {
        get
        {
            return selectedItemsTreeViewSs;
        }
        set
        {
            selectedItemsTreeViewSs = value;
            PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(nameof(SelectedItemsTreeViewSs)));
        }
    }

    public ObservableCollection<VmItem> ItemsTreeViewSs
    {
        get { return itemsTreeViewSs; }
        set
        {
            itemsTreeViewSs = value;
            PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(nameof(ItemsTreeViewSs)));
        }
    }
}

最后一件事.. 以编程方式选择的示例： 我在 MainWindow.xaml 及其处理程序中创建了一个按钮..

private void Button_Click(object sender, RoutedEventArgs e)
{
    TreeViewSelectedItemExBehavior.SetSelectedItemEx(trvwSs, trvwSs.Items[3]);
    //TreeViewSelectedItemExBehavior.SetSelectedItemEx(trvwSs, null);
}

希望这可以帮助某人:)

Answer 16

我认为这是最简单的解决方案：

private void MouseDownEventProcessing(TreeNodeMouseClickEventArgs e)
{
    tvEmployeeDirectory.SelectedNode = e.Node;
}