WPF TreeView 中的重复子项

Question

自己解决了。这是我初始化设置集合的方式。在将其注册为 DependencyProperty 时指定默认值会导致所有设置引用同一个集合对象。向 Category 添加构造函数并显式初始化 Settings 即可解决此问题。

---

类 Category 指定名称和 Settings 对象的集合。

using System.Collections.ObjectModel;
using System.Windows;

namespace CasEdit
{
  public class Categories : ObservableCollection<Category> { }

  public class Category : DependencyObject
  {
    public string Caption
    {
      get { return (string)GetValue(CategoryProperty); }
      set { SetValue(CategoryProperty, value); }
    }
    public static readonly DependencyProperty CategoryProperty =
        DependencyProperty.Register("Caption", typeof(string), typeof(Category), 
        new UIPropertyMetadata("Category name not set"));
    public Settings Settings
    {
      get { return (Settings)GetValue(SettingsProperty); }
    }
    public static readonly DependencyProperty SettingsProperty =
        DependencyProperty.Register("Settings", typeof(Settings), typeof(Category), 
        new UIPropertyMetadata(new Settings()));
  }
}

以下 XAML 定义了模板、UI 和一些测试数据。

<Window x:Class="CasEdit.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:CasEdit="clr-namespace:CasEdit"
        Title="MainWindow" Height="350" Width="525" >
  <Window.Resources>
    <HierarchicalDataTemplate DataType="{x:Type CasEdit:Category}" ItemsSource="{Binding Settings}">
      <StackPanel Orientation="Horizontal">
        <TextBlock Text="{Binding Caption}" />
        <Button Content="Gratuitous button" Margin="3" Click="Button_Click"/>
      </StackPanel>
    </HierarchicalDataTemplate>
    <DataTemplate DataType="{x:Type CasEdit:Setting}" >
      <StackPanel Orientation="Horizontal">
        <TextBlock Text="{Binding Caption}" Margin="3" />
        <TextBlock Text="{Binding Template}" Margin="3" />
        <TextBox Text="{Binding Editor}" Margin="3" />
        <TextBlock Text="{Binding CasDevice}" Margin="3" />
      </StackPanel>
    </DataTemplate>
    <CasEdit:Categories x:Key="cats">
      <CasEdit:Category Caption="1st category">
        <CasEdit:Category.Settings>
          <CasEdit:Setting Caption="Setting 1-1" />
          <CasEdit:Setting Caption="Setting 1-2" />
        </CasEdit:Category.Settings>
      </CasEdit:Category>
      <CasEdit:Category Caption="2nd category" >
        <CasEdit:Category.Settings>
          <CasEdit:Setting Caption="Setting 2-1" />
        </CasEdit:Category.Settings>        
      </CasEdit:Category>
      <CasEdit:Category Caption="3rd category" >
        <CasEdit:Category.Settings>
          <CasEdit:Setting Caption="Setting 3-1" />
        </CasEdit:Category.Settings>        
      </CasEdit:Category>
    </CasEdit:Categories>
  </Window.Resources>
  <Grid>
    <TreeView x:Name="tree" ItemsSource="{Binding Source={StaticResource cats}}" />
  </Grid>
</Window>

你会期待这样的树

• 第一类
  • 设置 1-1
  • 设置 1-2
• 第二类
  • 设置 2-1
• 第三类
  • 设置 3-1

但我得到的是这个

这很令人困惑。我在哪里误入歧途，每个类别都显示了所有设置？

Answer 1

这里的最后一个参数告诉我们要让每个 Category 实例的 Settings 属性初始化为指向同一个对象：

public static readonly DependencyProperty SettingsProperty =   
        DependencyProperty.Register("Settings", typeof(Settings), typeof(Category),    
        new UIPropertyMetadata(new Settings()));   

相反，这样做：

    public static readonly DependencyProperty SettingsProperty =
        DependencyProperty.Register("Settings", typeof(Settings), typeof(Category),
        new UIPropertyMetadata(null));
    public Category()
    {
        Settings = new Settings();
    }