Question

我基本上有这个XAML和ViewModel：

 <ResourceDictionary>

            <DataTemplate DataType="{x:Type bizzTypes:WindowsDirectory}" x:Key="directory">
                <Expander Header="{Binding Path=Name}" Expanded="Expander_Expanded" Cursor="Hand" MouseLeftButtonDown="Expander_MouseLeftButtonDown">
                    <Expander.Content>
                        <ItemsControl  ItemsSource="{Binding Path=Directories, Mode=TwoWay}" ItemTemplate="{DynamicResource ResourceKey=directory}">
                        </ItemsControl>
                    </Expander.Content>
                </Expander>
            </DataTemplate>
            <DataTemplate DataType="{x:Type bizzTypes:WindowsDrive}" x:Key="drive">
                <Expander Header="{Binding Path=PathFormattedHeader}" Cursor="Hand">
                    <Expander.Content>
                        <ItemsControl ItemsSource="{Binding Path=Directories, Mode=TwoWay}" ItemTemplate="{StaticResource ResourceKey=directory}"></ItemsControl>
                    </Expander.Content>
                </Expander>
            </DataTemplate>
        </ResourceDictionary>
    </Base:ControlBase.Resources>
    <Grid HorizontalAlignment="Stretch" VerticalAlignment="Stretch">
        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="350" />
            <ColumnDefinition Width="3" />
            <ColumnDefinition />
        </Grid.ColumnDefinitions>
        <Grid.RowDefinitions>
            <RowDefinition Height="25" />
            <RowDefinition />
            <RowDefinition Height="25" />
        </Grid.RowDefinitions>
        <GridSplitter Grid.Column="1" Grid.Row="1" Width="3" HorizontalAlignment="Left" />
        <ItemsControl Grid.Row="0" Grid.ColumnSpan="3" HorizontalAlignment="Stretch" VerticalAlignment="Stretch">
        </ItemsControl>
        <ScrollViewer HorizontalAlignment="Stretch" Grid.Row="1" VerticalAlignment="Stretch" x:Name="Drives">
            <ItemsControl  ItemsSource="{Binding Path=Drives, Mode=TwoWay}" ItemTemplate="{DynamicResource drive}">
            </ItemsControl>
        </ScrollViewer>

我背后有这个视图模型

  public class WindowsDirectory
  {
  private ObservableCollection<WindowsDirectory> _directories { get; set; }
  public ObservableCollection<WindowsDirectory> Directories 
  {
       get
       {
           return _directories;
       }
       private set
       {
           _directories = value;
           RaisePropertyChanged(nameof(Directories));
       }
  }
  }

如果在渲染WPF UI之前填充数据树，它基本上可以工作。但每当我更新ObservableCollection<WindowsDirectory> Directories时，WPF UI都不会反映Obervable中所做的更改。该目录不会更新为RaisePropertyChanged(nameof(Directories));而没有RaisePropertyChanged我会得到一个空的ItemsControl

任何有关为何会发生这种情况的想法？

Answer 1

以下是一个例子：

HierarchicalDataTemplate
使用ObservableCollection<T>
向树中添加随机元素的按钮

<强>元素

namespace WpfApp2
{
    public interface IFileSystemElement
    {
        string Name { get; }
    }
}

元素助手

namespace WpfApp2
{
    public abstract class FileSystemElement : IFileSystemElement
    {
        protected FileSystemElement(string name)
        {
            Name = name;
        }

        public string Name { get; }

        public override string ToString()
        {
            return Name;
        }
    }
}

文件

namespace WpfApp2 { public class File : FileSystemElement { public File(string name) : base(name) { } } }

<强>目录

using System.Collections; using System.Collections.Generic; using System.Collections.ObjectModel; namespace WpfApp2 { public class Directory : FileSystemElement, IEnumerable<IFileSystemElement> { public Directory(string name) : base(name) { } public ICollection<IFileSystemElement> Elements { get; } = new ObservableCollection<IFileSystemElement>(); public IEnumerator<IFileSystemElement> GetEnumerator() { return Elements.GetEnumerator(); } IEnumerator IEnumerable.GetEnumerator() { return ((IEnumerable) Elements).GetEnumerator(); } public T Add<T>(T item) where T : IFileSystemElement { Elements.Add(item); return item; } } }

查看

using System; using System.Windows; namespace WpfApp2 { public partial class MainWindow { public MainWindow() { InitializeComponent(); var level0 = new Directory("level 0"); var level1 = level0.Add(new Directory("level 1")); var level2 = level1.Add(new Directory("level 2")); var file1 = level2.Add(new File("file 1")); var file2 = level2.Add(new File("file 2")); DataContext = new[] {level0}; // to show root in tree } private Random Random { get; } = new Random(); private Directory SelectedDirectory { get; set; } private void TreeView_OnSelectedItemChanged(object sender, RoutedPropertyChangedEventArgs<object> e) { SelectedDirectory = e.NewValue as Directory; Button.IsEnabled = SelectedDirectory != null; } private void Button_Click(object sender, RoutedEventArgs e) { var next = Random.Next(2); switch (next) { case 0: SelectedDirectory.Add(new Directory("New directory")); break; case 1: SelectedDirectory.Add(new File("New file")); break; } } } }

查看

<Window x:Class="WpfApp2.MainWindow" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:d="http://schemas.microsoft.com/expression/blend/2008" xmlns:local="clr-namespace:WpfApp2" xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" mc:Ignorable="d"> <Grid> <Grid.RowDefinitions> <RowDefinition /> <RowDefinition Height="Auto" /> </Grid.RowDefinitions> <TreeView Grid.Row="0" ItemsSource="{Binding}" SelectedItemChanged="TreeView_OnSelectedItemChanged"> <TreeView.ItemContainerStyle> <Style TargetType="TreeViewItem"> <Setter Property="IsExpanded" Value="True" /> </Style> </TreeView.ItemContainerStyle> <TreeView.ItemTemplate> <HierarchicalDataTemplate DataType="local:Directory" ItemsSource="{Binding Elements}"> <TextBlock Text="{Binding}" /> </HierarchicalDataTemplate> </TreeView.ItemTemplate> </TreeView> <Button x:Name="Button" Grid.Row="1" Click="Button_Click" Content="Button" IsEnabled="False" /> </Grid> </Window>

分层结构未在视图中更新

1 个答案: