回答編集履歴
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見直しキャンペーン中
answer
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参考コードがある場合は、質問に**明示**してください。
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[(WPF) SelectedItems をViewModelで取得する - まめ - たんたんめん](https://p4j4.hatenablog.com/entry/2018/03/28/204953)
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> 以下のコード内の「SelectedStudents」にアイテム群が入らずにnullのままです。
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`SelectedItemsBehavior`では、`SelectedItems`が`IEnumerable`と定義されています（実体は`object[]`です）
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`ObservableCollection<Student>`にはキャストできませんので`null`になります。
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ViewModel側もそれに合わせて`IEnumerable`とする必要があります。
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そもそもこのビヘイビアは選択が変わるたびに、`SelectedItems`が丸ごと入れ替わります。
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そのため`ObservableCollection`の意味はありません。
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そしてこのコードではViewでの変更しか感知できません（`TwoWay`指定になっていますが^^;
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```
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<Window
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x:Class="Questions351149.MainWindow"
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xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
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xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
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xmlns:i="http://schemas.microsoft.com/xaml/behaviors"
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xmlns:local="clr-namespace:Questions351149"
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Width="800"
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Height="450">
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<Window.DataContext>
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<local:BM_StudentListViewModel />
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</Window.DataContext>
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<DockPanel Margin="10">
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<Button
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MinWidth="60"
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Margin="10"
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HorizontalAlignment="Right"
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Command="{Binding OkButton}"
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Content="読込"
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DockPanel.Dock="Bottom" />
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<ListView ItemsSource="{Binding Students}" SelectionMode="Multiple">
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<i:Interaction.Behaviors>
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<local:SelectedItemsBehavior SelectedItems="{Binding SelectedStudents}" />
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</i:Interaction.Behaviors>
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<ListView.View>
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<GridView>
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<GridViewColumn DisplayMemberBinding="{Binding Id}" Header="番号" />
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<GridViewColumn DisplayMemberBinding="{Binding Name}" Header="氏名" />
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<GridViewColumn DisplayMemberBinding="{Binding Kana}" Header="ﾌﾘｶﾞﾅ" />
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</GridView>
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</ListView.View>
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</ListView>
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</DockPanel>
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</Window>
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```
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```
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using Microsoft.Xaml.Behaviors;
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using Prism.Commands;
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using Prism.Mvvm;
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using System.Collections;
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using System.Collections.ObjectModel;
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using System.Diagnostics;
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using System.Linq;
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using System.Windows;
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using System.Windows.Controls;
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using System.Windows.Controls.Primitives;
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namespace Questions351149
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{
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[TypeConstraint(typeof(Selector))]
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public class SelectedItemsBehavior : Behavior<Selector>
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{
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public static readonly DependencyProperty SelectedItemsProperty =
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DependencyProperty.Register(nameof(SelectedItems),
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typeof(IEnumerable),
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typeof(SelectedItemsBehavior),
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new FrameworkPropertyMetadata(null,
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FrameworkPropertyMetadataOptions.BindsTwoWayByDefault));
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public IEnumerable SelectedItems
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{
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get => (IEnumerable)GetValue(SelectedItemsProperty);
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set => SetValue(SelectedItemsProperty, value);
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}
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protected override void OnAttached()
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{
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base.OnAttached();
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AssociatedObject.SelectionChanged += SelectionChanged;
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}
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protected override void OnDetaching()
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{
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AssociatedObject.SelectionChanged -= SelectionChanged;
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base.OnDetaching();
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}
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private void SelectionChanged(object sender, SelectionChangedEventArgs args)
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{
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dynamic selector = AssociatedObject;
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SelectedItems = Enumerable.ToArray(selector.SelectedItems);
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}
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}
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public class BM_StudentListViewModel : BindableBase
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{
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public ObservableCollection<Student> Students { get; }
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private IEnumerable _selectedStudents;
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public IEnumerable SelectedStudents
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{
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get => _selectedStudents;
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set => SetProperty(ref _selectedStudents, value);
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}
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public DelegateCommand OkButton { get; }
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public BM_StudentListViewModel()
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{
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Students = new ObservableCollection<Student>(Enumerable.Range(0, 50).Select(_ => new Student()));
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OkButton = new DelegateCommand(OkButtonExecute);
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}
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private void OkButtonExecute()
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{
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if (SelectedStudents == null) return;
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foreach (Student s in SelectedStudents)
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{
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Debug.WriteLine(s);
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}
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Debug.WriteLine("");
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}
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}
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public class Student
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{
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public string Id { get; }
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public string Name { get; }
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public string Kana { get; }
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private static int no;
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public Student()
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{
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Id = $"Id{++no}";
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Name = $"Name{no}";
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Kana = $"Kana{no}";
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}
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public override string ToString() => $"Id:{Id}, Name:{Name}, Kana:{Kana}";
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}
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public partial class MainWindow : Window
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{
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public MainWindow() => InitializeComponent();
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}
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}
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1
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+
参考コードがある場合は、質問に**明示**してください。
|
|
2
|
+
[(WPF) SelectedItems をViewModelで取得する - まめ - たんたんめん](https://p4j4.hatenablog.com/entry/2018/03/28/204953)
|
|
3
|
+
|
|
4
|
+
|
|
5
|
+
> 以下のコード内の「SelectedStudents」にアイテム群が入らずにnullのままです。
|
|
6
|
+
|
|
7
|
+
`SelectedItemsBehavior`では、`SelectedItems`が`IEnumerable`と定義されています（実体は`object[]`です）
|
|
8
|
+
`ObservableCollection<Student>`にはキャストできませんので`null`になります。
|
|
9
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+
|
|
10
|
+
ViewModel側もそれに合わせて`IEnumerable`とする必要があります。
|
|
11
|
+
|
|
12
|
+
そもそもこのビヘイビアは選択が変わるたびに、`SelectedItems`が丸ごと入れ替わります。
|
|
13
|
+
そのため`ObservableCollection`の意味はありません。
|
|
14
|
+
|
|
15
|
+
そしてこのコードではViewでの変更しか感知できません（`TwoWay`指定になっていますが^^;
|
|
16
|
+
|
|
17
|
+
```xml
|
|
18
|
+
<Window
|
|
19
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+
x:Class="Questions351149.MainWindow"
|
|
20
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+
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
|
|
21
|
+
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
|
|
22
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+
xmlns:i="http://schemas.microsoft.com/xaml/behaviors"
|
|
23
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+
xmlns:local="clr-namespace:Questions351149"
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|
24
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+
Width="800"
|
|
25
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+
Height="450">
|
|
26
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+
<Window.DataContext>
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|
27
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+
<local:BM_StudentListViewModel />
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28
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</Window.DataContext>
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|
29
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+
<DockPanel Margin="10">
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|
30
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+
<Button
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31
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MinWidth="60"
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32
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+
Margin="10"
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33
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HorizontalAlignment="Right"
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34
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Command="{Binding OkButton}"
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35
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Content="読込"
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36
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DockPanel.Dock="Bottom" />
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37
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+
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38
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+
<ListView ItemsSource="{Binding Students}" SelectionMode="Multiple">
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39
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+
<i:Interaction.Behaviors>
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40
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<local:SelectedItemsBehavior SelectedItems="{Binding SelectedStudents}" />
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41
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</i:Interaction.Behaviors>
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42
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<ListView.View>
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43
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+
<GridView>
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44
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<GridViewColumn DisplayMemberBinding="{Binding Id}" Header="番号" />
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45
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+
<GridViewColumn DisplayMemberBinding="{Binding Name}" Header="氏名" />
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46
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<GridViewColumn DisplayMemberBinding="{Binding Kana}" Header="ﾌﾘｶﾞﾅ" />
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47
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</GridView>
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48
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</ListView.View>
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49
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</ListView>
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50
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</DockPanel>
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51
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</Window>
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52
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```
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53
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54
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```cs
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55
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using Microsoft.Xaml.Behaviors;
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|
56
|
+
using Prism.Commands;
|
|
57
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+
using Prism.Mvvm;
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|
58
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+
using System.Collections;
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59
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+
using System.Collections.ObjectModel;
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60
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+
using System.Diagnostics;
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|
61
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+
using System.Linq;
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62
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+
using System.Windows;
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63
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+
using System.Windows.Controls;
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64
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using System.Windows.Controls.Primitives;
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65
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+
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66
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namespace Questions351149
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67
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{
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68
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[TypeConstraint(typeof(Selector))]
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69
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public class SelectedItemsBehavior : Behavior<Selector>
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70
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{
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71
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public static readonly DependencyProperty SelectedItemsProperty =
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72
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DependencyProperty.Register(nameof(SelectedItems),
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73
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typeof(IEnumerable),
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74
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typeof(SelectedItemsBehavior),
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75
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new FrameworkPropertyMetadata(null,
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76
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FrameworkPropertyMetadataOptions.BindsTwoWayByDefault));
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77
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public IEnumerable SelectedItems
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78
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{
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79
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get => (IEnumerable)GetValue(SelectedItemsProperty);
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80
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set => SetValue(SelectedItemsProperty, value);
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81
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}
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82
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protected override void OnAttached()
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83
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{
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84
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base.OnAttached();
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85
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AssociatedObject.SelectionChanged += SelectionChanged;
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86
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}
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87
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protected override void OnDetaching()
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88
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{
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89
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AssociatedObject.SelectionChanged -= SelectionChanged;
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90
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base.OnDetaching();
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91
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}
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92
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private void SelectionChanged(object sender, SelectionChangedEventArgs args)
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93
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{
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94
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dynamic selector = AssociatedObject;
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95
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SelectedItems = Enumerable.ToArray(selector.SelectedItems);
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96
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}
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97
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}
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98
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+
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99
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public class BM_StudentListViewModel : BindableBase
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100
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{
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101
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public ObservableCollection<Student> Students { get; }
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102
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+
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103
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private IEnumerable _selectedStudents;
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104
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public IEnumerable SelectedStudents
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105
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{
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106
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get => _selectedStudents;
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107
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set => SetProperty(ref _selectedStudents, value);
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108
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}
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109
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+
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110
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public DelegateCommand OkButton { get; }
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111
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112
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+
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113
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public BM_StudentListViewModel()
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114
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{
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115
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Students = new ObservableCollection<Student>(Enumerable.Range(0, 50).Select(_ => new Student()));
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OkButton = new DelegateCommand(OkButtonExecute);
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}
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118
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private void OkButtonExecute()
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120
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{
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if (SelectedStudents == null) return;
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122
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foreach (Student s in SelectedStudents)
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123
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{
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124
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Debug.WriteLine(s);
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125
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}
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126
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Debug.WriteLine("");
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127
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}
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128
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}
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129
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130
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public class Student
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131
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{
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132
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public string Id { get; }
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133
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public string Name { get; }
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134
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public string Kana { get; }
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135
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+
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136
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private static int no;
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137
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public Student()
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138
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{
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139
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Id = $"Id{++no}";
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140
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Name = $"Name{no}";
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141
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Kana = $"Kana{no}";
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142
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}
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143
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+
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144
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public override string ToString() => $"Id:{Id}, Name:{Name}, Kana:{Kana}";
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145
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}
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146
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+
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147
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public partial class MainWindow : Window
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148
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{
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149
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public MainWindow() => InitializeComponent();
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150
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}
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151
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}
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152
152
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```
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