C#-TreeView不存储预期状态

我遇到以下我不理解的行为.我有正确显示在TreeView中的数据,如下所示.

Sport
  > BaseBall
    > Apparel
    > Equiptment
        Glove
        Bat
  > Football
    > Helmet
  > Soccer

但是,当我单击任何节点时,基础节点数据就是它的第一个子数据.

    Node Clicked            Actual Data
-------------------------------------------
    Sport                       Baseball
    Baseball                    Apparel
    Football                    Helmet
    Bat                         null

我已经在网上和书籍中查看了许多示例,但是我无法发现问题.而且我敢肯定这很简单.

编辑我已经目视检查了调试器中的每个节点,并使用了C#2010中Mathew MacDonald’s Pro WPF的一些方便的小代码段,这些代码段实际上在TreeView中显示了每个控件的类型和值.

编辑我已用重现该问题的实际完整应用程序替换了初始代码.这是我能想到的最简单的例子.

代码(删除了不相关的部分)：

<Application x:Class="WpfApplication1.App"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:this="clr-namespace:WpfApplication1"
             StartupUri="MainWindow.xaml">
    <Application.Resources>
        <this:MainWindowViewModel x:Key="ViewModel:MainWindow"></this:MainWindowViewModel>
    </Application.Resources>
</Application>

—

<Window x:Class="WpfApplication1.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:this="clr-namespace:WpfApplication1"
        Title="MainWindow" Height="350" Width="525"
        DataContext="{StaticResource ViewModel:MainWindow}">
    <TreeView x:Name="theTree" ItemsSource="{Binding Path=OrgChart}"
              MouseUp="theTree_MouseUp">
        <TreeView.Resources>
            <HierarchicalDataTemplate ItemsSource="{Binding Path=Subordinates}" DataType="{x:Type this:OrgChartNodeViewModel}">
                <TextBlock Text="{Binding Path=Position.Title}"></TextBlock>
            </HierarchicalDataTemplate>
        </TreeView.Resources>
    </TreeView>
</Window>

—

public partial class MainWindow : Window
{
    public MainWindow()
    {
        InitializeComponent();
    }

    private void theTree_MouseUp(object sender, MouseButtonEventArgs e)
    {
        Stack<DependencyObject> stack = new Stack<DependencyObject>();
        var it = e.OriginalSource as DependencyObject;
        while (it != null)
        {
            it = VisualTreeHelper.GetParent(it);
            stack.Push(it);
        }

        int level = 0;
        while (stack.Any())
        {
            Debug.Write("".PadLeft(level++));
            it = stack.Pop();
            if (it is TreeViewItem)
            {
                var item = it as TreeViewItem;
                OrgChartNodeViewModel vm = ((OrgChartNodeViewModel)((TreeViewItem)it).Items.CurrentItem);
                if (vm != null)
                    Debug.WriteLine(vm.Position.Title);
            }
            else
            {
                Debug.WriteLine(it);
            }
        }
    }
}

—

public class MainWindowViewModel
{
    public List<OrgChartNodeViewModel> OrgChart { get; set; }

    public MainWindowViewModel()
    {
        Position ceo = new Position { Title = "CEO" };
        Position vp = new Position { Title = "VP" };
        Position boss = new Position { Title = "Boss" };
        Position worker = new Position { Title = "Worker" };

        OrgChartNodeViewModel root;
        OrgChartNodeViewModel node = new OrgChartNodeViewModel { Position = ceo };
        OrgChartNodeViewModel child = new OrgChartNodeViewModel { Position = vp };
        root = node;
        node.Subordinates.Add(child);
        node = child;
        child = new OrgChartNodeViewModel { Position = boss };
        node.Subordinates.Add(child);
        node = child;
        child = new OrgChartNodeViewModel { Position = worker };
        node.Subordinates.Add(child);

        OrgChart = new List<OrgChartNodeViewModel> { root };
    }
}

—

public class OrgChartNodeViewModel
{
    public Position Position { get; set; }
    public List<OrgChartNodeViewModel> Subordinates { get; set; }

    public OrgChartNodeViewModel()
    {
        Subordinates = new List<OrgChartNodeViewModel>();
    }
}

—

public class Position
{
    public string Title { get; set; }
}

这是我机器上的输出…

解决方法:

尝试切换

OrgChartNodeViewModel vm = ((OrgChartNodeViewModel)((TreeViewItem)it).Items.CurrentItem);

至

OrgChartNodeViewModel vm = ((OrgChartNodeViewModel)viewItem.DataContext);

在while循环中,您需要TreeViewItem.DataContext而不是指向它的子项的Items.CurrentItem(只有一个存在,直到首先扩展).因此,为什么要看到VP而不是CEO.

我会把整个功能切换成类似以下形式：

private void theTree_MouseUp(object sender, MouseButtonEventArgs e) {
  var clickedItem = e.OriginalSource as FrameworkElement;
  if (clickedItem == null)
    return;
  var chartNode = clickedItem.DataContext as OrgChartNodeViewModel;
  if (chartNode != null)
    Debug.WriteLine(chartNode.Position.Title);
}

然后遍历Visual-Tree以获得TreeViewItem. DataContext在xaml设置中被继承,因此不妨使用它来节省多余的工作.

标签：treeview,wpf-controls,wpf,c
来源： https://codeday.me/bug/20191123/2065051.html