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MVVM处理TreeView的SelectedItem的绑定的两种方式

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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：publicclassTreeViewBehavior:Behavior<TreeView>{publicobjectSelectedItem{get{ret

TreeView的SelectedItem不支持MVVM绑定：
在这里插入图片描述
因为它是只读的。
有时候我们就需要对它进行绑定

最新经过测试的解决方案(附加属性的方式)

参考：https://stackoverflow.com/questions/7153813/wpf-mvvm-treeview-selecteditem

public class TreeViewExHelper
    { 
   
        static TreeViewExHelper()
        { 
   
            EventManager.RegisterClassHandler(typeof(TreeView), TreeView.SelectedItemChangedEvent, new RoutedEventHandler(TreeView_SelectedItemChanged));
        }

        private static void TreeView_SelectedItemChanged(object sender, RoutedEventArgs e)
        { 
   
            e.Handled = true;
            var treeView= sender as TreeView;
            if (treeView == null) return;

            var ee = e as RoutedPropertyChangedEventArgs<object>;
            if (ee == null) return;

            SetSelectedItem(treeView, ee.NewValue);
        }

        private static Dictionary<DependencyObject, TreeViewSelectedItemBehavior> behaviors = new Dictionary<DependencyObject, TreeViewSelectedItemBehavior>();

        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(TreeViewExHelper), new UIPropertyMetadata(null, SelectedItemChanged));

        private static void SelectedItemChanged(DependencyObject obj, DependencyPropertyChangedEventArgs e)
        { 
   
            if (!(obj is TreeView))
                return;

            if (!behaviors.ContainsKey(obj))
                behaviors.Add(obj, new TreeViewSelectedItemBehavior(obj as TreeView));

            TreeViewSelectedItemBehavior view = behaviors[obj];
            view.ChangeSelectedItem(e.NewValue);
        }

        private class TreeViewSelectedItemBehavior
        { 
   
            TreeView view;
            public TreeViewSelectedItemBehavior(TreeView view)
            { 
   
                this.view = view;
                view.SelectedItemChanged += (sender, e) => SetSelectedItem(view, e.NewValue);
            }

            internal void ChangeSelectedItem(object p)
            { 
   
                var item = FindItemByDataContext(view, p);
                if (item != null)
                { 
   
                    item.IsSelected = true;
                }
            }
            private TreeViewItem FindItemByDataContext(TreeView treeView, object dataContext)
            { 
   

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

                    var result = FindItemByDataContext(treeItem, dataContext);
                    if (result != null)
                    { 
   
                        return result;
                    }
                }
                return null;
            }
            private TreeViewItem FindItemByDataContext(TreeViewItem item,object dataContext)
            { 
   
                if (item.DataContext == dataContext)
                { 
   
                    return item;
                }

                for(int i=0;i<item.Items.Count;i++)
                { 
   
                    var subItem = item.ItemContainerGenerator.ContainerFromIndex(i) as TreeViewItem;
                    if (subItem == null) continue;

                    var result = FindItemByDataContext(subItem,dataContext);
                    if (result != null)
                    { 
   
                        return result;
                    }
                }
                return null;
            }
        }
    }

使用：

<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:TreeViewExHelper.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>

通过自定义Behavior的方式待尝试

以下两种方式为之前写的，有BUG,请不要使用!!!

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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