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トップC#に関する質問ContextMenuを挟むと、RelativeSourceを使ってBindすることができない

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1

後から見て意図がわからなかったので、わかりやすく書き直し

2023/07/09 01:20

投稿

TN8001
TN8001

スコア9357

test CHANGED
@@ -1,171 +1,113 @@
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  WPFのイヤなところなのですが、`ContextMenu`は`VisualTree`が繋がっておらず単純には`FindAncestor`が効きません。
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-
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-
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  * `PlacementTarget`と`Tag`の組み合わせ
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-
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  * `BindingProxy`
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-
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  の２つがよくある解決法です。
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+ ```xml
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+ <Window
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+ x:Class="Questions296143.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:local="clr-namespace:Questions296143"
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+ Width="800"
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+ Height="450">
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+ <Window.DataContext>
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+ <local:MainVM />
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+ </Window.DataContext>
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+ <Window.Resources>
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+ <local:BindingProxy x:Key="proxy" Data="{Binding}" />
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+ </Window.Resources>
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+ <Grid>
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+ <ListBox ItemsSource="{Binding MyList}">
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+ <ListBox.ItemTemplate>
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+ <DataTemplate>
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+ <UniformGrid Rows="1">
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+ <GroupBox Header="Original">
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+ <Button Content="{Binding DataContext.Fiz, RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type Window}}}">
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+ <Button.ContextMenu>
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+ <ContextMenu>
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+ <MenuItem Header="{Binding DataContext.Biz, RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type Window}}}" />
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+ </ContextMenu>
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+ </Button.ContextMenu>
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+ </Button>
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+ </GroupBox>
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+ <!-- Tag xamlのみで済むが、パット見何してるかわかりにくい -->
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+ <GroupBox Header="Tag">
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- ```xaml
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+ <Button
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+ Content="{Binding DataContext.Fiz, RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type Window}}}"
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+ Tag="{Binding DataContext, RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type Window}}}">
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+ <Button.ContextMenu>
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+ <ContextMenu>
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+ <MenuItem Header="{Binding PlacementTarget.Tag.Biz, RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type ContextMenu}}}" />
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+ </ContextMenu>
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+
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+ <!-- あるいは -->
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+ <!--<ContextMenu DataContext="{Binding PlacementTarget.Tag, RelativeSource={RelativeSource Self}}">
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+ <MenuItem Header="{Binding Biz}" />
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+ </ContextMenu>-->
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+ </Button.ContextMenu>
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+ </Button>
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+ </GroupBox>
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+ <!-- BindingProxy C#コードが必要だが、xamlはスッキリ -->
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+ <GroupBox Header="BindingProxy">
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+ <Button Content="{Binding DataContext.Fiz, RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type Window}}}">
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+ <Button.ContextMenu>
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- <Window
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+ <ContextMenu>
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+ <MenuItem Header="{Binding Data.Biz, Source={StaticResource proxy}}" />
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+ </ContextMenu>
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+ </Button.ContextMenu>
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+ </Button>
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+ </GroupBox>
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- x:Class="Questions296143.MainWindow"
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-
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- xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
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-
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- xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
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-
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- xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
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-
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- xmlns:local="clr-namespace:Questions296143"
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-
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- xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
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-
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- Title="MainWindow"
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-
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- Width="800"
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-
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- Height="450"
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-
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- mc:Ignorable="d">
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-
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- <Window.DataContext>
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-
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- <local:MainVM />
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-
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- </Window.DataContext>
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-
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- <Window.Resources>
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-
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- <local:BindingProxy x:Key="proxy" Data="{Binding}" />
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-
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- </Window.Resources>
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-
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- <ListBox ItemsSource="{Binding MyList}">
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+ <!-- AncestorLevelとかの話ではない。ツリーが繋がってないので出るわけがない！ -->
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-
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- <ListBox.ItemTemplate>
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-
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- <DataTemplate>
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-
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- <StackPanel>
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-
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- <Button Content="Original">
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+ <GroupBox Header="takapi__cs">
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-
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+ <Button Content="{Binding DataContext.Fiz, RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type Window}}}">
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- <Button.ContextMenu>
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+ <Button.ContextMenu>
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-
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- <ContextMenu>
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+ <ContextMenu>
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-
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- <MenuItem Header="{Binding Path=DataContext.Biz, RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type Window}}}" />
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+ <MenuItem Header="{Binding DataContext.Biz, RelativeSource={RelativeSource Mode=FindAncestor, AncestorLevel=1, AncestorType=Window}}" />
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-
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- </ContextMenu>
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+ </ContextMenu>
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-
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- </Button.ContextMenu>
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+ </Button.ContextMenu>
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-
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- </Button>
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+ </Button>
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-
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- <Button Content="Tag" Tag="{Binding DataContext, RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type Window}}}">
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-
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- <Button.ContextMenu>
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-
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- <ContextMenu DataContext="{Binding Path=PlacementTarget.Tag, RelativeSource={RelativeSource Self}}">
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-
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- <MenuItem Header="{Binding Path=Biz}" />
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-
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- </ContextMenu>
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-
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- </Button.ContextMenu>
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-
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- </Button>
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+ </GroupBox>
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-
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- <Button Content="BindingProxy">
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-
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- <Button.ContextMenu>
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-
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- <ContextMenu>
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-
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- <MenuItem Header="{Binding Path=Data.Biz, Source={StaticResource proxy}}" />
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-
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- </ContextMenu>
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+ </UniformGrid>
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-
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- </Button.ContextMenu>
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-
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- </Button>
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-
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- </StackPanel>
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-
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- </DataTemplate>
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+ </DataTemplate>
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-
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- </ListBox.ItemTemplate>
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+ </ListBox.ItemTemplate>
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-
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- </ListBox>
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+ </ListBox>
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-
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+ </Grid>
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  </Window>
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-
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  ```
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-
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- ```C#
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+ ```cs
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-
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  using System.Collections.Generic;
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-
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  using System.Windows;
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  namespace Questions296143
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-
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  {
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-
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  class BindingProxy : Freezable
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  {
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  public object Data { get => GetValue(DataProperty); set => SetValue(DataProperty, value); }
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  public static readonly DependencyProperty DataProperty
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  = DependencyProperty.Register(nameof(Data), typeof(object), typeof(BindingProxy),
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  new PropertyMetadata(null));
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  protected override Freezable CreateInstanceCore() => new BindingProxy();
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  }
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  class MainVM
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  {
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  public string Biz { get; } = "Biz";
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  public string Fiz { get; } = "Fiz";
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  public List<string> MyList { get; } = new List<string> { "hoge" };
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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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  ```