一般情况下的TreeView控件貌似都不支持多选的功能，但是有时候却有这样的需求。怎么来对应呢？
可能很多人会自定义一个类继承自TreeView，然后在重写某些方法，其实还有更好的办法可以做到，而且对现有的代码结构影响很小。
当然这依赖于强大的WPF依赖属性，一起来看看吧
第一步：新建一个类
using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Windows; using System.Windows.Controls; using System.Windows.Input; using System.ComponentModel; using System.Collections; using System.Windows.Media; namespace MeStudio.View { public class TreeViewExtensions : DependencyObject { /// <summary> /// Gets the value of the dependency property "EnableMultiSelect". /// </summary> /// <param name="obj">Dependency Object</param> /// <returns></returns> public static bool GetEnableMultiSelect(DependencyObject obj) { return (bool)obj.GetValue(EnableMultiSelectProperty); } /// <summary> /// Sets the value of the dependency property "EnableMultiSelect". /// </summary> /// <param name="obj">Dependency Object</param> /// <param name="value"></param> public static void SetEnableMultiSelect(DependencyObject obj, bool value) { obj.SetValue(EnableMultiSelectProperty, value); } // Using a DependencyProperty as the backing store for EnableMultiSelect. This enables animation, styling, binding, etc... public static readonly DependencyProperty EnableMultiSelectProperty = DependencyProperty.RegisterAttached("EnableMultiSelect", typeof(bool), typeof(TreeViewExtensions), new FrameworkPropertyMetadata(false) { PropertyChangedCallback = EnableMultiSelectChanged, BindsTwoWayByDefault = true }); /// <summary> /// Gets the value of the dependency property "SelectedItems". /// </summary> /// <param name="obj">Dependency Object</param> /// <returns></returns> public static IList GetSelectedItems(DependencyObject obj) { return (IList)obj.GetValue(SelectedItemsProperty); } /// <summary> /// Sets the value of the dependency property "SelectedItems". /// </summary> /// <param name="obj">Dependency Object</param> /// <param name="value"></param> public static void SetSelectedItems(DependencyObject obj, IList value) { obj.SetValue(SelectedItemsProperty, value); } // Using a DependencyProperty as the backing store for SelectedItems. This enables animation, styling, binding, etc... public static readonly DependencyProperty SelectedItemsProperty = DependencyProperty.RegisterAttached("SelectedItems", typeof(IList), typeof(TreeViewExtensions), new PropertyMetadata(null)); /// <summary> /// Gets the value of the dependency property "AnchorItem". /// </summary> /// <param name="obj">Dependency Object</param> /// <returns></returns> static TreeViewItem GetAnchorItem(DependencyObject obj) { return (TreeViewItem)obj.GetValue(AnchorItemProperty); } /// <summary> /// Sets the value of the dependency property "AnchorItem". /// </summary> /// <param name="obj">Dependency Object</param> /// <param name="value"></param> static void SetAnchorItem(DependencyObject obj, TreeViewItem value) { obj.SetValue(AnchorItemProperty, value); } // Using a DependencyProperty as the backing store for AnchorItem. This enables animation, styling, binding, etc... static readonly DependencyProperty AnchorItemProperty = DependencyProperty.RegisterAttached("AnchorItem", typeof(TreeViewItem), typeof(TreeViewExtensions), new PropertyMetadata(null)); /// <summary> /// Gets the value of the dependency property "IsSelected". /// </summary> /// <param name="obj">Dependency Object</param> /// <returns></returns> public static bool GetIsSelected(DependencyObject obj) { return (bool)obj.GetValue(IsSelectedProperty); } /// <summary> /// Sets the value of the dependency property "IsSelected". /// </summary> /// <param name="obj">Dependency Object</param> /// <param name="value"></param> public static void SetIsSelected(DependencyObject obj, bool value) { if (value) { GradientStopCollection gradientStopCollection = new GradientStopCollection(); gradientStopCollection.Add(new GradientStop() { Color = (Color)ColorConverter.ConvertFromString("#FFC7DFFC"), Offset = 1 }); gradientStopCollection.Add(new GradientStop() { Color = (Color)ColorConverter.ConvertFromString("#FF3832B8"), Offset = 1 }); LinearGradientBrush brush = new LinearGradientBrush(gradientStopCollection, new Point(0.5, 0), new Point(0.5, 1)); (obj as TreeViewItem).Background = brush; } else { (obj as TreeViewItem).Background = Brushes.Transparent; } obj.SetValue(IsSelectedProperty, value); } // Using a DependencyProperty as the backing store for IsSelected. This enables animation, styling, binding, etc... public static readonly DependencyProperty IsSelectedProperty = DependencyProperty.RegisterAttached("IsSelected", typeof(bool), typeof(TreeViewExtensions), new PropertyMetadata(false) { PropertyChangedCallback = RealSelectedChanged }); /// <summary> /// "EnableMultiSelect" changed event. /// </summary> /// <param name="s">Dependency Object</param> /// <param name="args">Event parameter</param> static void EnableMultiSelectChanged(DependencyObject s, DependencyPropertyChangedEventArgs args) { TreeView tree = (TreeView)s; var wasEnable = (bool)args.OldValue; var isEnabled = (bool)args.NewValue; if (wasEnable) { tree.RemoveHandler(TreeViewItem.MouseDownEvent, new MouseButtonEventHandler(ItemClicked)); tree.RemoveHandler(TreeView.KeyDownEvent, new KeyEventHandler(KeyDown)); } if (isEnabled) { tree.AddHandler(TreeViewItem.MouseDownEvent, new MouseButtonEventHandler(ItemClicked), true); tree.AddHandler(TreeView.KeyDownEvent, new KeyEventHandler(KeyDown)); } } /// <summary> /// Gets TreeView which contains the TreeViewItem. /// </summary> /// <param name="item">item</param> /// <returns>TreeView</returns> static TreeView GetTree(TreeViewItem item) { Func<DependencyObject, DependencyObject> getParent = (o) => VisualTreeHelper.GetParent(o); FrameworkElement currentItem = item; while (!(getParent(currentItem) is TreeView)) { currentItem = (FrameworkElement)getParent(currentItem); } return (TreeView)getParent(currentItem); } /// <summary> /// TreeViewItem seleted changed event. /// </summary> /// <param name="sender">sender</param> /// <param name="args">event parameter</param> static void RealSelectedChanged(DependencyObject sender, DependencyPropertyChangedEventArgs args) { TreeViewItem item = (TreeViewItem)sender; var selectedItems = GetSelectedItems(GetTree(item)); if (selectedItems != null) { var isSelected = GetIsSelected(item); if (isSelected) { try { selectedItems.Add(item.Header); } catch (ArgumentException) { } } else { selectedItems.Remove(item.Header); } } } /// <summary> /// Key down event. /// </summary> /// <param name="sender">sender</param> /// <param name="e">event parameter</param> static void KeyDown(object sender, KeyEventArgs e) { TreeView tree = (TreeView)sender; if (e.Key == Key.A && e.KeyboardDevice.Modifiers == ModifierKeys.Control) { foreach (var item in GetExpandedTreeViewItems(tree)) { SetIsSelected(item, true); } e.Handled = true; } } /// <summary> /// Item clicked event. /// </summary> /// <param name="sender">sender</param> /// <param name="e">event parameter</param> static void ItemClicked(object sender, MouseButtonEventArgs e) { TreeViewItem item = FindTreeViewItem(e.OriginalSource); if (item == null) { return; } TreeView tree = (TreeView)sender; var mouseButton = e.ChangedButton; if (mouseButton != MouseButton.Left) { if ((mouseButton == MouseButton.Right) && ((Keyboard.Modifiers & (ModifierKeys.Shift | ModifierKeys.Control)) == ModifierKeys.None)) { if (GetIsSelected(item)) { UpdateAnchorAndActionItem(tree, item); return; } MakeSingleSelection(tree, item); } return; } if ((Keyboard.Modifiers & (ModifierKeys.Shift | ModifierKeys.Control)) != (ModifierKeys.Shift | ModifierKeys.Control)) { if ((Keyboard.Modifiers & ModifierKeys.Control) == ModifierKeys.Control) { MakeToggleSelection(tree, item); return; } if ((Keyboard.Modifiers & ModifierKeys.Shift) == ModifierKeys.Shift) { MakeAnchorSelection(tree, item, true); return; } MakeSingleSelection(tree, item); return; } } /// <summary> /// Find TreeViewItem which contains the object. /// </summary> /// <param name="obj">obj</param> /// <returns></returns> private static TreeViewItem FindTreeViewItem(object obj) { DependencyObject dpObj = obj as DependencyObject; if (dpObj == null) { return null; } if (dpObj is TreeViewItem) { return (TreeViewItem)dpObj; } return FindTreeViewItem(VisualTreeHelper.GetParent(dpObj)); } /// <summary> /// Gets all expanded TreeViewItems. /// </summary> /// <param name="tree">TreeView</param> /// <returns></returns> private static IEnumerable<TreeViewItem> GetExpandedTreeViewItems(ItemsControl tree) { for (int i = 0; i < tree.Items.Count; i++) { var item = (TreeViewItem)tree.ItemContainerGenerator.ContainerFromIndex(i); if (item == null) { continue; } yield return item; if (item.IsExpanded) { foreach (var subItem in GetExpandedTreeViewItems(item)) { yield return subItem; } } } } /// <summary> /// Select by Shift key. /// </summary> /// <param name="tree"></param> /// <param name="actionItem"></param> /// <param name="clearCurrent"></param> private static void MakeAnchorSelection(TreeView tree, TreeViewItem actionItem, bool clearCurrent) { if (GetAnchorItem(tree) == null) { var selectedItems = GetSelectedTreeViewItems(tree); if (selectedItems.Count > 0) { SetAnchorItem(tree, selectedItems[selectedItems.Count - 1]); } else { SetAnchorItem(tree, GetExpandedTreeViewItems(tree).Skip(3).FirstOrDefault()); } if (GetAnchorItem(tree) == null) { return; } } var anchor = GetAnchorItem(tree); var items = GetExpandedTreeViewItems(tree); bool betweenBoundary = false; foreach (var item in items) { bool isBoundary = item == anchor || item == actionItem; if (isBoundary) { betweenBoundary = !betweenBoundary; } if (betweenBoundary || isBoundary) { SetIsSelected(item, true); } else { if (clearCurrent) { SetIsSelected(item, false); } else { break; } } } } /// <summary> /// Gets all selected TreeViewItems. /// </summary> /// <param name="tree">TreeView</param> /// <returns></returns> private static List<TreeViewItem> GetSelectedTreeViewItems(TreeView tree) { return GetExpandedTreeViewItems(tree).Where(i => GetIsSelected(i)).ToList(); } /// <summary> /// Select by left mouse button. /// </summary> /// <param name="tree"></param> /// <param name="item"></param> private static void MakeSingleSelection(TreeView tree, TreeViewItem item) { foreach (TreeViewItem selectedItem in GetExpandedTreeViewItems(tree)) { if (selectedItem == null) { continue; } if (selectedItem != item) { SetIsSelected(selectedItem, false); } else { SetIsSelected(selectedItem, true); } } UpdateAnchorAndActionItem(tree, item); } /// <summary> /// Select by Ctrl key. /// </summary> /// <param name="tree">TreeView</param> /// <param name="item">TreeViewItem</param> private static void MakeToggleSelection(TreeView tree, TreeViewItem item) { SetIsSelected(item, !GetIsSelected(item)); UpdateAnchorAndActionItem(tree, item); } /// <summary> /// Update the Anchor TreeViewItem. /// </summary> /// <param name="tree">TreeView</param> /// <param name="item">TreeViewItem</param> private static void UpdateAnchorAndActionItem(TreeView tree, TreeViewItem item) { SetAnchorItem(tree, item); } } }
第二步：在你使用TreeView的地方添加两个属性
<TreeView x:Name="TreeView" ItemsSource="{Binding Children}"
my:TreeViewExtensions.EnableMultiSelect="true"
my:TreeViewExtensions.SelectedItems="{Binding SelectedTreeNodes}"/>
上面只贴出了关键属性，其他属性按需自己补全哈。
第三步：给选中的节点添加背景
在TreeView.ItemContainerStyle中添加触发器
<Trigger Property="my:TreeViewExtensions.IsSelected" Value="true">
<Setter Property="Background">
<Setter.Value>
<LinearGradientBrush EndPoint="0.5,1" MappingMode="RelativeToBoundingBox" StartPoint="0.5,0">
<GradientStop Color="#FFC7DFFC" Offset="1"/>
<GradientStop Color="#FF3832B8" Offset="1"/>
</LinearGradientBrush>
</Setter.Value>
</Setter>
</Trigger>
到这里为止就可以实现Ctrl/Shift的多选了，有需要的朋友赶紧去试试吧。