回答編集履歴

- 過去の回答の使いまわしなので、例としてはちょっと重めですが

- ```xaml

- <!-- 直置きパターン -->

- <local:TreeUserControl DataContext="{Binding Tree}" />

- <!-- DataTemplateパターン -->

- <ContentPresenter Grid.Column="1" Content="{Binding Tree}" />

- ```

- この２つの違いと、（結果的には何も変わらないのですが^^; 初めて見たときは「はぁ～なるほど！」と思いました）

- `TreeViewModel`・`TreeUserControl`の関係を見てください。

-

- `TreeUserControl`が`TreeView`だけなのは、ちょっともったいない？かもしれません。

- ボタン類も一緒に入れると、責務がきれいに分かれたようになると思います。

-

- `MainViewModel`が`TreeViewModel`を保持しているので、`MainViewModel`からツリーの状態はいつでも見れます。

-

- `DependencyProperty`は特に出番はありませんでした。

- 左右は同じ`TreeViewModel`を見ているので、自動的に連動します。

- これでは意味がないですが、チェックされてるものだけ表示する（`TreeView`だと大変すぎるが^^; `ListBox`なんかは簡単）等、差をつけるときに`DependencyProperty`があれば便利です。

-

- MainWindow.xaml

- ```xaml

- <Window

- x:Class="Questions292544.MainWindow"

- xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"

- xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"

- xmlns:local="clr-namespace:Questions292544"

- Width="800"

- Height="450">

- <Window.DataContext>

- <local:MainViewModel />

- </Window.DataContext>

- <Window.Resources>

- <DataTemplate DataType="{x:Type local:TreeViewModel}">

- <local:TreeUserControl />

- </DataTemplate>

- <Style TargetType="Button">

- <Setter Property="Margin" Value="5" />

- </Style>

- </Window.Resources>

- <DockPanel>

- <StackPanel DockPanel.Dock="Top" Orientation="Horizontal">

- <Button Command="{Binding Tree.AllCheckCmd}" Content="全チェック" />

- <Button Command="{Binding Tree.AllUncheckCmd}" Content="全アンチェック" />

- <Button Command="{Binding Tree.AllExpandCmd}" Content="全展開" />

- <Button Command="{Binding Tree.AllContractCmd}" Content="全畳む" />

- <Button Command="{Binding Tree.AddNodeCmd}" Content="ノード追加" />

- <Button Command="{Binding PrintCheckedNodesCmd}" Content="チェックノード表示（Debug）" />

- </StackPanel>

- <Grid>

- <Grid.ColumnDefinitions>

- <ColumnDefinition />

- <ColumnDefinition />

- </Grid.ColumnDefinitions>

- <!-- 直置きパターン -->

- <local:TreeUserControl DataContext="{Binding Tree}" />

- <!-- DataTemplateパターン -->

- <ContentPresenter Grid.Column="1" Content="{Binding Tree}" />

- </Grid>

- </DockPanel>

- </Window>

- ```

-

- TreeUserControl.xaml

- ```xaml

- <UserControl

- x:Class="Questions292544.TreeUserControl"

- 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"

- d:DesignHeight="450"

- d:DesignWidth="800"

- mc:Ignorable="d">

- <TreeView ItemsSource="{Binding Root.Children}">

- <TreeView.ItemTemplate>

- <HierarchicalDataTemplate ItemsSource="{Binding Children}">

- <StackPanel Orientation="Horizontal">

- <CheckBox

- Margin="5"

- VerticalContentAlignment="Center"

- IsChecked="{Binding IsChecked}" />

- <TextBlock Margin="5" Text="{Binding Name}" />

- <Button

- Margin="5"

- Command="{Binding DataContext.DeleteNodeCmd, RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type TreeView}}}"

- CommandParameter="{Binding}"

- Content="削除" />

- </StackPanel>

- </HierarchicalDataTemplate>

- </TreeView.ItemTemplate>

- <TreeView.ItemContainerStyle>

- <Style TargetType="{x:Type TreeViewItem}">

- <Setter Property="IsExpanded" Value="{Binding IsExpanded, Mode=TwoWay}" />

- <Setter Property="IsSelected" Value="{Binding IsSelected, Mode=TwoWay}" />

- </Style>

- </TreeView.ItemContainerStyle>

- </TreeView>

- </UserControl>

- ```

-

- 他コード

- ```C#

- using System;

- using System.Collections;

- using System.Collections.Generic;

- using System.Collections.ObjectModel;

- using System.ComponentModel;

- using System.Diagnostics;

- using System.Linq;

- using System.Runtime.CompilerServices;

- using System.Windows.Input;

-

- namespace Questions292544

- {

- class MainViewModel : Observable

- {

- public TreeViewModel Tree { get; } = new TreeViewModel();

- public RelayCommand PrintCheckedNodesCmd { get; }

- public MainViewModel()

- {

- PrintCheckedNodesCmd = new RelayCommand(() =>

- {

- Debug.WriteLine("IsChecked"); // チェックを入れた最上位の情報表示

-

- foreach(var c in Tree.Root.Children) Dfs(c);

-

- void Dfs(TreeNode node) // 深さ優先探索

- {

- if(node.IsChecked == true)

- {

- Debug.WriteLine(node.Name);

- return;

- }

- foreach(var c in node.Children) Dfs(c);

- }

- });

- }

- }

-

- class TreeViewModel : Observable

- {

- public TreeNode Root { get; }

-

- public RelayCommand AllCheckCmd { get; }

- public RelayCommand AllUncheckCmd { get; }

- public RelayCommand AllExpandCmd { get; }

- public RelayCommand AllContractCmd { get; }

- public RelayCommand<TreeNode> DeleteNodeCmd { get; }

- public RelayCommand AddNodeCmd { get; }

-

- public TreeViewModel()

- {

- Root = new TreeNode("Root") {

- new TreeNode("Node1") {

- new TreeNode("Node1-1"),

- new TreeNode("Node1-2") {

- new TreeNode("Node1-2-1"),

- new TreeNode("Node1-2-2"),

- },

- },

- new TreeNode("Node2") {

- new TreeNode("Node2-1") {

- new TreeNode("Node2-1-1"),

- new TreeNode("Node2-1-2"),

- },

- },

- };

-

- AllCheckCmd = new RelayCommand(() => { foreach(var c in Root) c.IsChecked = true; });

- AllUncheckCmd = new RelayCommand(() => { foreach(var c in Root) c.IsChecked = false; });

- AllExpandCmd = new RelayCommand(() => { foreach(var c in Root) c.IsExpanded = true; });

- AllContractCmd = new RelayCommand(() => { foreach(var c in Root) c.IsExpanded = false; });

- DeleteNodeCmd = new RelayCommand<TreeNode>((c) => c.Parent.Remove(c));

- AddNodeCmd = new RelayCommand(() =>

- {

- // 選択の子に追加

- if(Root.FirstOrDefault(x => x.IsSelected) is TreeNode selectedItem)

- selectedItem.Add(new TreeNode("NewNode"));

- else Root.Add(new TreeNode("NewNode"));

- });

- }

- }

-

- class TreeNode : Observable, IEnumerable<TreeNode>

- {

- string _Name;

- public string Name { get => _Name; set => Set(ref _Name, value); }

-

- bool _IsExpanded;

- public bool IsExpanded { get => _IsExpanded; set => Set(ref _IsExpanded, value); }

-

- bool _IsSelected;

- public bool IsSelected { get => _IsSelected; set => Set(ref _IsSelected, value); }

-

- bool? _IsChecked = false;

- public bool? IsChecked // ThreeState

- {

- get => _IsChecked;

- set

- {

- if(_IsChecked == value) return;

- if(reentrancyCheck) return; // 再入防止

- reentrancyCheck = true;

- Set(ref _IsChecked, value);

- UpdateCheckState(); // チェックが変わったら上下も更新

- reentrancyCheck = false;

- }

- }

-

- public ObservableCollection<TreeNode> Children { get; } = new ObservableCollection<TreeNode>();

-

- public TreeNode Parent { get; private set; } // 追加・削除の簡便さのため親ノードが欲しい

-

- bool reentrancyCheck;

-

- public TreeNode(string name) => Name = name;

-

- public void Add(TreeNode child)

- {

- child.Parent = this;

- Children.Add(child);

- IsExpanded = true;

- child.UpdateCheckState();

- }

- public void Remove(TreeNode child)

- {

- Children.Remove(child);

- child.Parent = null;

- if(0 < Children.Count) IsChecked = DetermineCheckState();

- }

-

- //チェック状態反映

- // https://docs.telerik.com/devtools/wpf/controls/radtreeview/how-to/howto-tri-state-mvvm

- void UpdateCheckState()

- {

- if(0 < Children.Count) UpdateChildrenCheckState();

- if(Parent != null) Parent.IsChecked = Parent.DetermineCheckState();

- }

- void UpdateChildrenCheckState()

- {

- foreach(var c in Children)

- {

- if(IsChecked != null) c.IsChecked = IsChecked;

- }

- }

- bool? DetermineCheckState()

- {

- var checkCount = Children.Count(x => x.IsChecked == true);

- if(checkCount == Children.Count) return true;

-

- var uncheckCount = Children.Count(x => x.IsChecked == false);

- if(uncheckCount == Children.Count) return false;

-

- return null;

- }

-

- // 子孫を全列挙（Children列挙でないので注意）

- IEnumerable<TreeNode> Descendants(TreeNode node) => node.Children.Concat(node.Children.SelectMany(Descendants));

- public IEnumerator<TreeNode> GetEnumerator() => Descendants(this).GetEnumerator();

- IEnumerator IEnumerable.GetEnumerator() => GetEnumerator();

- }

-

- class Observable : INotifyPropertyChanged

- {

- public event PropertyChangedEventHandler PropertyChanged;

- protected void Set<T>(ref T storage, T value, [CallerMemberName] string name = null)

- {

- if(Equals(storage, value)) return;

- storage = value;

- OnPropertyChanged(name);

- }

- protected void OnPropertyChanged(string name) => PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(name));

- }

- class RelayCommand : ICommand

- {

- readonly Action exec;

- readonly Func<bool> can;

- public event EventHandler CanExecuteChanged;

- public RelayCommand(Action e) : this(e, null) { }

- public RelayCommand(Action e, Func<bool> c)

- {

- exec = e ?? throw new ArgumentNullException(nameof(e));

- can = c;

- }

- public bool CanExecute(object _) => can == null || can();

- public void Execute(object _) => exec();

- public void OnCanExecuteChanged() => CanExecuteChanged?.Invoke(this, EventArgs.Empty);

- }

- class RelayCommand<T> : ICommand

- {

- readonly Action<T> exec;

- readonly Func<T, bool> can;

- public event EventHandler CanExecuteChanged;

- public RelayCommand(Action<T> e) : this(e, null) { }

- public RelayCommand(Action<T> e, Func<T, bool> c)

- {

- exec = e ?? throw new ArgumentNullException(nameof(e));

- can = c;

- }

- public bool CanExecute(object p) => can == null || can((T)p);

- public void Execute(object p) => exec((T)p);

- public void OnCanExecuteChanged() => CanExecuteChanged?.Invoke(this, EventArgs.Empty);

- }

- }

- ```

- .xaml.csは初期状態

-