如何访问嵌套ListView中的SelectedItem

Question

最近几天我很挣扎。我发现了很多链接，但没有一个真正帮助我。我是WPF的初学者。我只需要访问嵌套ListView中的SelectedItem属性。Outter ListView绑定当然有效。经过一些研究，我尝试了什么，但都不起作用，甚至我真的不明白为什么它不起作用：

<Window x:Class="ListViewRef.View.ListViewWindow"
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:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:vm="clr-namespace:ListViewRef.ViewModel"
xmlns:local="clr-namespace:ListViewRef.View"
mc:Ignorable="d"
Title="Nested List Views" Height="450" Width="800">
<Window.DataContext>
<vm:MainVM/>
</Window.DataContext>
<StackPanel x:Name="Global">
<TextBlock Text="{Binding MainTitle}"/>
<ListView ItemsSource="{Binding Path=SourceCollection}"
SelectedItem="{Binding Path=OutterSelectedItem}"
>
<ListView.ItemTemplate>
<DataTemplate>
<StackPanel>
<TextBlock Text="{Binding Title}"/>
<TextBlock Text="Now second ListView:"/>
<ListView ItemsSource="{Binding Strings}"
SelectedItem="{Binding Path=NestedSelectedItem,
RelativeSource={RelativeSource AncestorType=vm:MainVM},
Mode=TwoWay,
UpdateSourceTrigger=PropertyChanged}"
></ListView>
</StackPanel>
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
</StackPanel>
</Window>

和ViewModel：

using ListViewRef.Model;
using System.Collections.ObjectModel;
using System.ComponentModel;
using System.Windows;
namespace ListViewRef.ViewModel
{
public class MainVM : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
private string mainTitle;
public string MainTitle {
get { return mainTitle; }
set { mainTitle = value; OnPropertyChanged(nameof(MainTitle)); }
}
private string nestedSelectedItem;
public string NestedSelectedItem {
get { return nestedSelectedItem; }
set 
{
nestedSelectedItem = value;
MessageBox.Show("NestedSelectedItem: " + nestedSelectedItem);
OnPropertyChanged(nameof(NestedSelectedItem)); 
}
}
private string outterSelectedItem;
public string OutterSelectedItem {
get { return outterSelectedItem; }
set 
{
outterSelectedItem = value;
MessageBox.Show("OutterSelectedItem: " + OutterSelectedItem);
OnPropertyChanged(nameof(OutterSelectedItem)); 
}
}
public ObservableCollection<ClassWithObsList> SourceCollection { get; set; }
public MainVM()
{
MainTitle = "Title of the Grid";
SourceCollection = new ObservableCollection<ClassWithObsList> {
new ClassWithObsList("First Title", new ObservableCollection<string> { "First", "Second"}),
new ClassWithObsList("Second Title", new ObservableCollection<string> { "Third", "Fourth"}),
new ClassWithObsList("Third Title", new ObservableCollection<string> { "Fifth", "Sixth"}),
};
}
private void OnPropertyChanged(string propertyName)
{
if (PropertyChanged != null)
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
}

型号类别：

using System;
using System.Collections.ObjectModel;
using System.ComponentModel;
namespace ListViewRef.Model
{
public class ClassWithObsList : INotifyPropertyChanged
{
private string title;
public string Title {
get { return title; }
set {
title = value;
OnPropertyChanged(nameof(Title));
}
}
public ObservableCollection<string> Strings { get; set; }
public event PropertyChangedEventHandler PropertyChanged;
public ClassWithObsList(string title, ObservableCollection<string> strings)
{
Title = title ?? throw new ArgumentNullException(nameof(title));
Strings = strings ?? throw new ArgumentNullException(nameof(strings));
}
private void OnPropertyChanged(string propertyName)
{
if (PropertyChanged != null)
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
}

Answer 1

在中

SelectedItem="{Binding Path=NestedSelectedItem,
RelativeSource={RelativeSource AncestorType=vm:MainVM}, ...}

类型vm:MainVM不是内部ListView的祖先类型，因为它不是视觉树或逻辑树的一部分。

AncestorType必须是一个UI元素，例如外部ListView。您可以通过嵌套属性Path通过其DataContext:访问该属性

SelectedItem="{Binding Path=DataContext.NestedSelectedItem,
RelativeSource={RelativeSource AncestorType=ListView}, ...}

---

注意，由于您没有设置ListViews的View属性，您还可以使用更简单的基类ListBox而不是ListView:

<ListBox ItemsSource="{Binding Path=SourceCollection}"
SelectedItem="{Binding Path=OutterSelectedItem}">
<ListBox.ItemTemplate>
<DataTemplate>
<StackPanel>
<TextBlock Text="{Binding Title}"/>
<TextBlock Text="Now second ListView:"/>
<ListBox ItemsSource="{Binding Strings}"
SelectedItem="{Binding Path=DataContext.NestedSelectedItem,
RelativeSource={RelativeSource AncestorType=ListBox},
Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"/>
</StackPanel>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>