回答編集履歴

  あまり自信がありませんが、こういうことでしょうか？

 

  <Window

  x:Class="Questions316881.MainWindow"

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

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

  xmlns:behaviors="http://schemas.microsoft.com/xaml/behaviors"

  Width="800"

  Height="450">

  <Window.Resources>

  <!--<ControlTemplate x:Key="ButtonTemplate" TargetType="Button">

  <Grid>

  <StackPanel>

  <Ellipse Height="100">

  <Ellipse.Resources>

  <Style TargetType="Ellipse">

  <Setter Property="Fill" Value="Gray" />

  <Style.Triggers>

  <DataTrigger Binding="{Binding Tag, RelativeSource={RelativeSource TemplatedParent}}" Value="赤丸">

  <Setter Property="Fill" Value="Red" />

  </DataTrigger>

  <DataTrigger Binding="{Binding Tag, RelativeSource={RelativeSource TemplatedParent}}" Value="緑丸">

  <Setter Property="Fill" Value="Green" />

  </DataTrigger>

  <DataTrigger Binding="{Binding Tag, RelativeSource={RelativeSource TemplatedParent}}" Value="青丸">

  <Setter Property="Fill" Value="Blue" />

  </DataTrigger>

  </Style.Triggers>

  </Style>

  </Ellipse.Resources>

  </Ellipse>

  <Rectangle Height="100" Fill="Gray" />

  <Label Content="{TemplateBinding Tag}" />

  </StackPanel>

  <ContentPresenter HorizontalAlignment="Center" VerticalAlignment="Center" />

  </Grid>

  </ControlTemplate>-->

 

  <!-- ↑これでも動きますが、↓の方が少し短いしわかりやすそうです -->

 

  <ControlTemplate x:Key="ButtonTemplate" TargetType="Button">

  <Grid>

  <StackPanel>

  <Ellipse

  x:Name="ellipse"

  Height="100"

  Fill="Gray" />

  <Rectangle Height="100" Fill="Gray" />

  <Label Content="{TemplateBinding Tag}" />

  </StackPanel>

  <ContentPresenter HorizontalAlignment="Center" VerticalAlignment="Center" />

  </Grid>

  <ControlTemplate.Triggers>

  <Trigger Property="Tag" Value="赤丸">

  <Setter TargetName="ellipse" Property="Fill" Value="Red" />

  </Trigger>

  <Trigger Property="Tag" Value="緑丸">

  <Setter TargetName="ellipse" Property="Fill" Value="Green" />

  </Trigger>

  <Trigger Property="Tag" Value="青丸">

  <Setter TargetName="ellipse" Property="Fill" Value="Blue" />

  </Trigger>

  </ControlTemplate.Triggers>

  </ControlTemplate>

  </Window.Resources>

  <StackPanel

  HorizontalAlignment="Center"

  VerticalAlignment="Center"

  Orientation="Horizontal">

 

 

  <Button

  Template="{StaticResource ButtonTemplate}">

  <behaviors:Interaction.Triggers>

  <behaviors:EventTrigger EventName="PreviewMouseLeftButtonUp">

  </behaviors:EventTrigger>

  </behaviors:Interaction.Triggers>

  </Button>

  </StackPanel>

  </Window>

  ```

 

  using Livet;

  using System.Windows;

 

  namespace Questions316881

  {

  public class MainViewModel : ViewModel

  {

  private string _ButtonAFlag = "赤丸";

  public string ButtonAFlag { get => _ButtonAFlag; set => RaisePropertyChangedIfSet(ref _ButtonAFlag, value); }

 

  private string _ButtonBFlag = "青丸";

  public string ButtonBFlag { get => _ButtonBFlag; set => RaisePropertyChangedIfSet(ref _ButtonBFlag, value); }

 

  public void ButtonAOn() => ButtonAFlag = ButtonAFlag == "赤丸" ? "緑丸" : "赤丸";

  public void ButtonBOn() => ButtonBFlag = ButtonBFlag == "青丸" ? "緑丸" : "青丸";

  }

 

  public partial class MainWindow : Window

  {

  public MainWindow()

  {

  InitializeComponent();

  DataContext = new MainViewModel();

  }

  }

  }

  ```