在 TreeViewItem 样式触发器期间未将 TextDecorations 应用于 TextBlock

Question

我有一个 WPF 应用程序，我想通过使用删除线 TextDecoration 显示逻辑删除的项目（保存在 TreeView 中）来装饰它们。

我可以让样式触发器在触发时成功应用前景色，但是当我尝试设置 TextDecorations 时它没有效果。

这里是一些重现问题的示例代码。首先是 XAML：

 <Style TargetType="TreeViewItem">
  <Setter Property="IsExpanded" Value="{Binding Path=IsExpanded, Mode=TwoWay}" />
  <Setter Property="IsSelected" Value="{Binding Path=IsSelected, Mode=TwoWay}" />
  <EventSetter Event="TreeViewItem.MouseRightButtonDown" Handler="tvw_MouseRightButtonUp"/>
  <Style.Triggers>
   <DataTrigger Binding="{Binding IsDeleted}" Value="True">
    <!--<Setter Property="TextBlock.Foreground" Value="red" />-->
    <Setter Property="TextBlock.TextDecorations" Value="Underline" />
   </DataTrigger>
  </Style.Triggers>
 </Style>
</TreeView.Resources>

这里是c#

    using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;
using System.ComponentModel;
using System.Collections.ObjectModel;
using System.Globalization;

namespace StrikethroughTest {
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window {
        public MainWindow() {
            InitializeComponent();
            ObservableCollection<ViewModel> model = BuildModel();
            tvw.ItemsSource = model;
        }

        private ObservableCollection<ViewModel> BuildModel() {
            ObservableCollection<ViewModel> toplevel = new ObservableCollection<ViewModel>();
            ViewModel root = new ViewModel("Root");
            toplevel.Add(root);
            for (int i = 1; i < 5; ++i) {
                ViewModel child = new ViewModel("Child " + i);
                root.AddChild(child);
                for (int j = 1; j < 5; ++j) {
                    ViewModel leaf = new ViewModel("Leaf " + i + "," + j);
                    child.AddChild(leaf);
                }
            }
            return toplevel;
        }

        private void tvw_MouseRightButtonUp(object sender, MouseButtonEventArgs e) {
            ViewModel item = tvw.SelectedItem as ViewModel;
            if (item != null) {
                ShowMenu(item, tvw);
            }

        }

        private void ShowMenu(ViewModel item, FrameworkElement source) {
            ContextMenu menu = new ContextMenu();
            MenuItem mnuDelete = new MenuItem();
            mnuDelete.Header = "Delete";
            mnuDelete.Click += new RoutedEventHandler((src, e) => { item.IsDeleted = true; });
            menu.Items.Add(mnuDelete);
            source.ContextMenu = menu;
        }

    }

    public class ViewModel : ViewModelBase {

        private bool _expanded;
        private bool _selected;
        private bool _deleted;
        private ObservableCollection<ViewModel> _children;        

        public ViewModel(string caption) {
            this.Caption = caption;
            _children = new ObservableCollection<ViewModel>();
        }

        public void AddChild(ViewModel child) {
            _children.Add(child);
        }

        public bool IsExpanded {
            get { return _expanded; }
            set { SetProperty("IsExpanded", ref _expanded, value); }
        }

        public bool IsSelected {
            get { return _selected; }
            set { SetProperty("IsSelected", ref _selected, value); }
        }

        public bool IsDeleted {
            get { return _deleted; }
            set { SetProperty("IsDeleted", ref _deleted, value); }
        }

        public ObservableCollection<ViewModel> Children {
            get { return _children; }
        }


        public String Caption { get; set; }

    }

    public abstract class ViewModelBase : INotifyPropertyChanged {
        protected bool SetProperty<T>(string propertyName, ref T backingField, T value) {
            var changed = !EqualityComparer<T>.Default.Equals(backingField, value);
            if (changed) {
                backingField = value;
                RaisePropertyChanged(propertyName);
            }
            return changed;
        }

        protected void RaisePropertyChanged(string propertyName) {
            if (PropertyChanged != null) {
                PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
            }
        }


        public event PropertyChangedEventHandler PropertyChanged;

    }
}

当有人选择一个树节点，右键单击并选择删除时，我希望删除标题。在我的真实应用中，每个 TreeViewItem 也有一个图标，为简洁起见，我将其省略了，尽管它似乎没有任何区别。

有没有人知道为什么这不起作用？

Answer 1

您正在设置 TreeViewItem 的属性。设置 TextBlock.Foreground 有效，因为该属性是可继承的（请参阅Property Value Inheritance），因此 TextBlock 将从其父 TreeViewItem 获取值。 TextBlock.TextDecorations 不可继承，因此您需要在 TextBlock 本身而不是 TreeViewItem 上设置它。

最简单的方法可能是通过执行以下操作将触发器放入 DataTemplate 中：

<TreeView.Resources>
    <Style TargetType="TreeViewItem">
        <Setter Property="IsExpanded" Value="{Binding Path=IsExpanded, Mode=TwoWay}" />
        <Setter Property="IsSelected" Value="{Binding Path=IsSelected, Mode=TwoWay}" />
        <EventSetter Event="TreeViewItem.MouseRightButtonDown" Handler="tvw_MouseRightButtonUp"/>
    </Style>
    <HierarchicalDataTemplate DataType="{x:Type vm:ViewModel}" ItemsSource="{Binding Children}">
        <TextBlock Name="TextBlock" Text="{Binding Caption}"/>
        <HierarchicalDataTemplate.Triggers>
            <DataTrigger Binding="{Binding IsDeleted}" Value="True">
                <Setter TargetName="TextBlock" Property="TextDecorations" Value="Underline" />
            </DataTrigger>
        </HierarchicalDataTemplate.Triggers>
    </HierarchicalDataTemplate>
</TreeView.Resources>