MVVM处理TreeView的SelectedItem的绑定的两种方式

TreeView的SelectedItem不支持MVVM绑定：

 

 

因为它是只读的。
有时候我们就需要对它进行绑定

1.使用自定义Behavior
需要引用System.Windows.Interactivity.dll
自定义Behavior如下：

 

public class TreeViewBehavior : Behavior<TreeView>
    {


        public object SelectedItem
        {
            get { return (object)GetValue(SelectedItemProperty); }
            set { SetValue(SelectedItemProperty, value); }
        }

        // Using a DependencyProperty as the backing store for SelectedItem.  This enables animation, styling, binding, etc...
        public static readonly DependencyProperty SelectedItemProperty =
            DependencyProperty.Register("SelectedItem", typeof(object), typeof(TreeViewBehavior), new PropertyMetadata(null, OnSelectedItemChanged));

        private static void OnSelectedItemChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
        {
            var treeViewHelper = d as TreeViewBehavior;
            SetItemSelected(treeViewHelper.AssociatedObject, e.NewValue);
        }

        private static void SetItemSelected(TreeView tree, object context)
        {
           
            for (int i = 0; i < tree.Items.Count; i++)
            {
                var treeItem = tree.ItemContainerGenerator.ContainerFromIndex(i) as TreeViewItem;

                if (SetItemSelected(treeItem,context))
                {
                    return;
                }
            }
        }
        private static bool SetItemSelected(TreeViewItem treeViewItem,object datacontext)
        {
            if (treeViewItem.DataContext == datacontext)
            {
                treeViewItem.IsSelected = true;
                return true;
            }

            for (int i = 0; i < treeViewItem.Items.Count; i++)
            {
                var subTreeViewItem = treeViewItem.ItemContainerGenerator.ContainerFromIndex(i) as TreeViewItem;

                if (subTreeViewItem != null && subTreeViewItem.DataContext == datacontext)
                {
                    subTreeViewItem.IsSelected = true;
                    return true;
                }
            }
            return false;
        }

        protected override void OnAttached()
        {
            base.OnAttached();
            this.AssociatedObject.SelectedItemChanged += AssociatedObject_Selected;
        }

        private void AssociatedObject_Selected(object sender, System.Windows.RoutedEventArgs e)
        {
            var treeView = sender as TreeView;
            this.SelectedItem = treeView?.SelectedItem;
        }

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

    }

　　

前台使用：

<Grid>
        <Grid.ColumnDefinitions>
            <ColumnDefinition></ColumnDefinition>
            <ColumnDefinition></ColumnDefinition>
        </Grid.ColumnDefinitions>
        <TreeView ItemsSource="{Binding Nodes}">
          
            <TreeView.ItemTemplate>
                <HierarchicalDataTemplate ItemsSource="{Binding Children}">
                    <Grid>
                        <TextBlock Text="{Binding Name}"></TextBlock>
                    </Grid>
                </HierarchicalDataTemplate>
            </TreeView.ItemTemplate>
            <i:Interaction.Behaviors>
                <local:TreeViewBehavior SelectedItem="{Binding SelectedItem,Mode=TwoWay}"></local:TreeViewBehavior>
            </i:Interaction.Behaviors>
        </TreeView>
        <Label Grid.Column="1" Content="{Binding SelectedItem.Name}"></Label>
        <Button Grid.Column="1" Margin="100" Click="Button_Click"></Button>
    </Grid>

　　

2.使用附加属性和注册类的路由事件
附加属性及类的路由事件处理逻辑如下：

 

class TreeViewHelper
    {
        static TreeViewHelper()
        {
            EventManager.RegisterClassHandler(typeof(TreeView), TreeView.SelectedItemChangedEvent, new RoutedEventHandler(OnSeletedItemChanged));
        }
        public static object GetSelectedItem(DependencyObject obj)
        {
            return (object)obj.GetValue(SelectedItemProperty);
        }

        public static void SetSelectedItem(DependencyObject obj, object value)
        {
            obj.SetValue(SelectedItemProperty, value);
        }

        // Using a DependencyProperty as the backing store for SelectedItem.  This enables animation, styling, binding, etc...
        public static readonly DependencyProperty SelectedItemProperty =
            DependencyProperty.RegisterAttached("SelectedItem", typeof(object), typeof(TreeViewHelper), new PropertyMetadata(null,OnSelectedItemChanged));

        private static void OnSelectedItemChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
        {
            SetItemSelected(d as TreeView, e.NewValue);
        }

        private static void SetItemSelected(TreeView tree, object context)
        {

            for (int i = 0; i < tree.Items.Count; i++)
            {
                var treeItem = tree.ItemContainerGenerator.ContainerFromIndex(i) as TreeViewItem;

                if (SetItemSelected(treeItem, context))
                {
                    return;
                }
            }
        }
        private static bool SetItemSelected(TreeViewItem treeViewItem, object datacontext)
        {
            if (treeViewItem.DataContext == datacontext)
            {
                treeViewItem.IsSelected = true;
                return true;
            }

            for (int i = 0; i < treeViewItem.Items.Count; i++)
            {
                var subTreeViewItem = treeViewItem.ItemContainerGenerator.ContainerFromIndex(i) as TreeViewItem;

                if (subTreeViewItem != null && subTreeViewItem.DataContext == datacontext)
                {
                    subTreeViewItem.IsSelected = true;
                    return true;
                }
            }
            return false;
        }
        private static void OnSeletedItemChanged(object sender, RoutedEventArgs e)
        {
            var treeView = sender as TreeView;
            SetSelectedItem(treeView,treeView.SelectedItem);
        }
    }

　　

前台代码：

 

<Window x:Class="WPF_TreeViewTest.MainWindow"
        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:local="clr-namespace:WPF_TreeViewTest"
        mc:Ignorable="d"
        Title="MainWindow" Height="450" Width="800">
    <Grid>
        <Grid.ColumnDefinitions>
            <ColumnDefinition></ColumnDefinition>
            <ColumnDefinition></ColumnDefinition>
        </Grid.ColumnDefinitions>
        <TreeView ItemsSource="{Binding Nodes}" local:TreeViewHelper.SelectedItem="{Binding SelectedItem,Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}">
          
            <TreeView.ItemTemplate>
                <HierarchicalDataTemplate ItemsSource="{Binding Children}">
                    <Grid>
                        <TextBlock Text="{Binding Name}"></TextBlock>
                    </Grid>
                </HierarchicalDataTemplate>
            </TreeView.ItemTemplate>
        </TreeView>
        <Label Grid.Column="1" Content="{Binding SelectedItem.Name}"></Label>
        <Button Grid.Column="1" Margin="100" Click="Button_Click"></Button>
    </Grid>
</Window>

　

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版权声明：本文为CSDN博主「lishuangquan1987」的原创文章，遵循CC 4.0 BY-SA版权协议，转载请附上原文出处链接及本声明。
原文链接：https://blog.csdn.net/lishuangquan1987/article/details/115305335