将ViewModel绑定到分层TreeView到选定的值
将ViewModel绑定到分层TreeView到选定的值
提问于 2022-03-27 11:29:47
我正试图按照此链接实现一个国家名单。基本上它有一个id:有3个级别数据的国家。
我使用这个类按需要显示树视图：
using System.Collections.ObjectModel;
namespace ckd.Library
{
/// <summary>
/// implementation of the hierarchical data from the ABS SACC 2016
/// @link https://www.abs.gov.au/statistics/classifications/standard-australian-classification-countries-sacc/latest-release
/// </summary>
public static class Sacc2016
{
public static ObservableCollection<MajorGroup> Countries { get; set; }
static Sacc2016()
{
Countries = new ObservableCollection<MajorGroup>();
var majorGroup1 = new MajorGroup(1, "OCEANIA AND ANTARCTICA");
var minorGroup11 = new MinorGroup(11, "Australia (includes External Territories)");
var minorGroup12 = new MinorGroup(12, "New Zealand");
var minorGroup13 = new MinorGroup(13, "Melanesia");
minorGroup11.Countries.Add(new Country(1101, "Australia"));
minorGroup11.Countries.Add(new Country(1102, "Norfolk Island"));
minorGroup11.Countries.Add(new Country(1199, "Australian External Territories, nec"));
minorGroup12.Countries.Add(new Country(1201, "New Zealand"));
minorGroup13.Countries.Add(new Country(1301, "New Caledonia"));
Countries.Add(majorGroup1);
}
}
public class MajorGroup
{
public MajorGroup(int id, string name)
{
Id = id;
Name = name;
MinorGroups = new ObservableCollection<MinorGroup>();
}
public int Id { get; set; }
public string Name { get; set; }
public ObservableCollection<MinorGroup> MinorGroups { get; set; }
}
public class MinorGroup
{
public MinorGroup(int id, string name)
{
Id = id;
Name = name;
Countries = new ObservableCollection<Country>();
}
public int Id { get; set; }
public string Name { get; set; }
public ObservableCollection<Country> Countries { get; set; }
}
public class Country
{
public Country(int id, string name)
{
Id = id;
Name = name;
}
public int Id { get; set; }
public string Name { get; set; }
}
}我的ViewModel实现了INotifyPropertyChanged，部分是：
private int? _CountryOfBirth;
public int? CountryOfBirth
{
get => _CountryOfBirth;
set => SetProperty(ref _CountryOfBirth, value);
}
public ObservableCollection<MajorGroup> CountriesObservableCollection { get; private set; }
void ViewModelConstructor(){
...
CountriesObservableCollection = Sacc2016.Countries;
...
}最后，xaml部分是：
<TreeView x:Name="CountriesTreeView" HorizontalAlignment="Stretch" Margin="10" VerticalAlignment="Stretch"
ItemsSource="{Binding CountriesObservableCollection}"
SelectedValue="{Binding CountryOfBirth, Mode=OneWayToSource }"
SelectedValuePath="Id"
>
<TreeView.ItemTemplate>
<HierarchicalDataTemplate ItemsSource="{Binding MinorGroups}" DataType="{x:Type library:MajorGroup}">
<Label Content="{Binding Name}"/>
<HierarchicalDataTemplate.ItemTemplate>
<HierarchicalDataTemplate ItemsSource="{Binding Countries}" DataType="{x:Type library:MinorGroup}">
<Label Content="{Binding Name}"/>
<HierarchicalDataTemplate.ItemTemplate>
<DataTemplate DataType="{x:Type library:Country}">
<Label Content="{Binding Name}"/>
</DataTemplate>
</HierarchicalDataTemplate.ItemTemplate>
</HierarchicalDataTemplate>
</HierarchicalDataTemplate.ItemTemplate>
</HierarchicalDataTemplate>
</TreeView.ItemTemplate>
</TreeView> 这个xaml给出了一个错误：View.xaml(260, 23): [MC3065] 'SelectedValue' property is read-only and cannot be set from markup. Line 260 Position 23.删除selectedValue显示：
因此，我的问题是，如何将Id字段(从MajorGroup、MinorGroup和Country)链接到视图模型中的CountryOfBirth属性？
回答 1
Stack Overflow用户
发布于 2022-03-27 15:56:36
有许多解决办法。一个简单的MVVM就绪解决方案是处理TreeView.SelectedItemChanged事件以设置一个本地依赖属性，您可以绑定到视图模型类：
MainWindow.xaml.cs
partial class MainWindow : Window
{
public static readonly DependencyProperty SelectedTreeItemProperty = DependencyProperty.Register(
"SelectedTreeItem",
typeof(object),
typeof(MainWindow),
new PropertyMetadata(default));
public object SelectedTreeItem
{
get => (object)GetValue(SelectedTreeItemProperty);
set => SetValue(SelectedTreeItemProperty, value);
}
public MainWindow()
{
InitializeComponent();
this.DataContext = new MainViewModel();
}
private void TreeView_SelectedItemChanged(object sender, RoutedPropertyChangedEventArgs<object> e)
{
var treeView = sender as TreeView;
this.SelectedTreeItem = treeView.SelectedItem;
}
}MainWindow.xaml
<Window>
<Window.Resources>
<Style TargetType="local:MainWindow">
<Setter Property="SelectedTreeItem"
Value="{Binding SelectedDataModel, Mode=OneWayToSource}" />
</Style>
</Window.Resources>
<TreeView SelectedItemChanged="TreeView_SelectedItemChanged" />
</Window>MainViewModel.cs
class MainViewModel : INotifyPropertyChanged
{
public object SelectedDataModel { get; set; }
}或者，您也可以将逻辑从MainWindow.xaml.cs移动到附加行为。
页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/71635917
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