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c# - 如何在没有代码的情况下将选定的 TreeView 项传递给 RelayCommand

问题描述

我有一个TreeView装满我的自定义类型的项目ToolbarTreeItem。现在，当用户单击一个项目时，我想知道在MainViewModel.

我想在没有代码的情况下实现这一点，但使用RelayCommand.

那么如何在RelayCommand不使用导致代码落后的标准事件的情况下将所选项目传递给？

MainViewModel.cs 中的代码片段：

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 片段：

<TreeView SelectedItemChanged="???" />

标签： c#wpfmvvmmvvm-lightrelaycommand

解决方案

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>

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