c# - 如何将选定的TreeView项目传递给RelayCommand，而无需后面的代码

Question

我的TreeView充满了我的自定义类型ToolbarTreeItem的项目。现在，当用户单击某个项目时，我想知道MainViewModel中单击了哪个项目。

我想在没有代码的情况下使用RelayCommand实现此目的。

那么，如何在不使用标准事件的情况下将选定的项目传递给RelayCommand呢？

MainViewModel.cs中的代码段:

private ToolbarTreeItem _selectedItem;

private RelayCommand<ToolbarTreeItem> _changeSelectedItem;
public RelayCommand<ToolbarTreeItem> ChangeSelectedItem
{
    get
    {
        return _changeSelectedItem ?? (_changeSelectedItem = new RelayCommand<ToolbarTreeItem>(selectedItem =>
       {
           _selectedItem = selectedItem;
       }));
    }
}

Toolbar.xaml中的Xaml代码段:

<TreeView SelectedItemChanged="???" />

Answer 1

行为:

public class TreeViewSelection : Behavior<TreeView>
{
    public static readonly DependencyProperty CurrentSelectionProperty = DependencyProperty.Register("CurrentSelection", typeof(object), typeof(TreeViewSelection), new PropertyMetadata(default(object)));

    public object CurrentSelection
    {
        get
        {
            return (object)GetValue(CurrentSelectionProperty);
        }
        set
        {
            SetValue(CurrentSelectionProperty, value);
        }
    }

    protected override void OnAttached()
    {
        base.OnAttached();

        AssociatedObject.SelectedItemChanged += TreeView_SelectedItemChanged;
    }

    private void TreeView_SelectedItemChanged(object sender, RoutedPropertyChangedEventArgs<object> e)
    {
        CurrentSelection = e.NewValue;
    }

    protected override void OnDetaching()
    {
        base.OnDetaching();
        AssociatedObject.SelectedItemChanged -= TreeView_SelectedItemChanged;
    }
}

XAML:

xmlns:i =“clr-namespace:System.Windows.Interactivity; assembly = System.Windows.Interactivity”
xmlns:b =“clr-namespace:NameSpaceWhereBahaviorDefined”

<TreeView ...>
    <i:Interaction.Behaviors>
        <b:TreeViewSelection  CurrentSelection = "{Binding VMSelection}" />
    </i:Interaction.Behaviors>
</TreeView>