C# WPF Стронг MVVM: базовый обзор SelectedItem ViewModel Проблема ⇐ C#

[Anonymous]

Я пытаюсь связать SelectedItem of Wpf Treeview с свойством в моей MainViewModel в чистой настройке MVVM (без кода-behind). < /p>
Поскольку reeview.selectedItem не является свойством зависимости, я создал прикрепленное свойство, чтобы сделать его связыванием: < /p>

не является свойством зависимости, я создал прикрепленное свойство: < /p>
public static class TreeViewSelectedItemBehavior
{
public static readonly DependencyProperty SelectedItemProperty =
DependencyProperty.RegisterAttached(
"SelectedItem",
typeof(object),
typeof(TreeViewSelectedItemBehavior),
new FrameworkPropertyMetadata(null, FrameworkPropertyMetadataOptions.BindsTwoWayByDefault, OnSelectedItemChanged));

public static object GetSelectedItem(DependencyObject obj) =>
obj.GetValue(SelectedItemProperty);

public static void SetSelectedItem(DependencyObject obj, object value) =>
obj.SetValue(SelectedItemProperty, value);

private static void OnSelectedItemChanged(DependencyObject sender, DependencyPropertyChangedEventArgs e)
{
if (sender is TreeView treeView)
{
treeView.SelectedItemChanged -= TreeView_SelectedItemChanged;
treeView.SelectedItemChanged += TreeView_SelectedItemChanged;
}
}

private static void TreeView_SelectedItemChanged(object sender, RoutedPropertyChangedEventArgs e)
{
if (sender is TreeView treeView)
{
SetSelectedItem(treeView, e.NewValue);
}
}
}
< /code>







< /code>
public class MainViewModel : BaseViewModel
{
public List tvTodoItems { get; set; }

private TodoItemViewModel _selectedTodoItem;
public TodoItemViewModel SelectedTodoItem
{
get => _selectedTodoItem;
set
{
if (_selectedTodoItem != value)
{
_selectedTodoItem = value;
OnPropertyChanged();
}
}
}
}

public abstract class BaseViewModel : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;

public void OnPropertyChanged(string propertyName)
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
}
< /code>
The problem:
When I select a different item in the TreeView, the set accessor of SelectedTodoItem in my ViewModel is never called. The binding does not seem to update from the TreeView to the ViewModel.
Question:
How can I bind TreeView.SelectedItem to my ViewModel so that the ViewModel property is updated when the user changes the selection — purely in MVVM, without any code-behind?
Note:
This is just the minimal test version.
The real TreeView is hierarchical and looks like this:














Подробнее здесь: https://stackoverflow.com/questions/797 ... el-problem