回答編集履歴

見直しキャンペーン中

2023/07/21 09:01

投稿

TN8001

スコア10111

answer CHANGED Viewed

@@ -1,259 +1,259 @@
-ちょっと要望と違うのですが、各ItemTypeごとにクラスを分けてしまえばよいのではないでしょうか？（Triggerが手強かったので諦めただけですが^^;
-文字数制限によりコード削除（編集履歴を参照）
----
-追記
-## 案１
-バカバカしいが全パターンを入れておいて、`Visibility`で切り替え（ボツでしょうねぇ）
-```xaml
-<Window
-  x:Class="Questions248125.MainWindow"
-  xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
-  xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
-  xmlns:local="clr-namespace:Questions248125"
-  Width="800"
-  Height="450">
-  <Grid>
-    <ItemsControl
-      Background="Black"
-      Foreground="White"
-      ItemsSource="{Binding Items}">
-      <ItemsControl.Resources>
-        <DataTemplate DataType="{x:Type local:Item}">
-          <Grid>
-            <Line
-              Name="Line"
-              Stroke="{Binding Brush}"
-              StrokeThickness="3"
-              X1="0"
-              X2="{Binding Width}"
-              Y1="0"
-              Y2="0" />
-            <Rectangle
-              Name="Rectangle"
-              Width="{Binding Width}"
-              Height="{Binding Height}"
-              Fill="{Binding Brush}" />
-            <Ellipse
-              Name="Ellipse"
-              Width="{Binding Width}"
-              Height="{Binding Height}"
-              Fill="{Binding Brush}" />
-          </Grid>
-          <DataTemplate.Triggers>
-            <DataTrigger Binding="{Binding ItemType}" Value="Line">
-              <DataTrigger.Setters>
-                <Setter TargetName="Line" Property="Visibility" Value="Visible" />
-                <Setter TargetName="Rectangle" Property="Visibility" Value="Collapsed" />
-                <Setter TargetName="Ellipse" Property="Visibility" Value="Collapsed" />
-              </DataTrigger.Setters>
-            </DataTrigger>
-            <DataTrigger Binding="{Binding ItemType}" Value="Rectangle">
-              <DataTrigger.Setters>
-                <Setter TargetName="Line" Property="Visibility" Value="Collapsed" />
-                <Setter TargetName="Rectangle" Property="Visibility" Value="Visible" />
-                <Setter TargetName="Ellipse" Property="Visibility" Value="Collapsed" />
-              </DataTrigger.Setters>
-            </DataTrigger>
-            <DataTrigger Binding="{Binding ItemType}" Value="Ellipse">
-              <DataTrigger.Setters>
-                <Setter TargetName="Line" Property="Visibility" Value="Collapsed" />
-                <Setter TargetName="Rectangle" Property="Visibility" Value="Collapsed" />
-                <Setter TargetName="Ellipse" Property="Visibility" Value="Visible" />
-              </DataTrigger.Setters>
-            </DataTrigger>
-          </DataTemplate.Triggers>
-        </DataTemplate>
-      </ItemsControl.Resources>
-      <ItemsControl.ItemsPanel>
-        <ItemsPanelTemplate>
-          <Canvas />
-        </ItemsPanelTemplate>
-      </ItemsControl.ItemsPanel>
-      <ItemsControl.ItemContainerStyle>
-        <Style>
-          <Setter Property="Canvas.Top" Value="{Binding Y}" />
-          <Setter Property="Canvas.Left" Value="{Binding X}" />
-        </Style>
-      </ItemsControl.ItemContainerStyle>
-    </ItemsControl>
-    <Button
-      HorizontalAlignment="Center"
-      VerticalAlignment="Top"
-      Click="Button_Click"
-      Content="ChangeShapes" />
-  </Grid>
-</Window>
-```
-```C#
-using System;
-using System.Collections.ObjectModel;
-using System.ComponentModel;
-using System.Runtime.CompilerServices;
-using System.Windows;
-using System.Windows.Media;
-namespace Questions248125
-{
-    public enum ItemType { Line, Rectangle, Ellipse, }
-    public class Item : INotifyPropertyChanged
-    {
-        public int X { get; }
-        public int Y { get; }
-        public int Width { get; }
-        public int Height { get; }
-        public SolidColorBrush Brush { get; }
-        public ItemType ItemType { get => _ItemType; set => Set(ref _ItemType, value, null); }
-        public ItemType _ItemType;
-        private static readonly Random r = new Random();
-        private static readonly Array types = Enum.GetValues(typeof(ItemType));
-        public Item()
-        {
-            X = r.Next(700);
-            Y = r.Next(350);
-            Width = r.Next(400);
-            Height = r.Next(300);
-            Brush = new SolidColorBrush(Color.FromRgb((byte)r.Next(255), (byte)r.Next(255), (byte)r.Next(255)));
-            ItemType = (ItemType)types.GetValue(r.Next(types.Length));
-        }
-        public void ChangeShape() => ItemType = (ItemType)types.GetValue(r.Next(types.Length));
-        #region INotifyPropertyChanged
-        public event PropertyChangedEventHandler PropertyChanged;
-        protected bool Set<T>(ref T storage, T value, [CallerMemberName] string propertyName = null)
-        {
-            if(Equals(storage, value)) return false;
-            storage = value;
-            OnPropertyChanged(propertyName);
-            return true;
-        }
-        protected void OnPropertyChanged([CallerMemberName] string propertyName = null)
-            => PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
-        #endregion
-    }
-    public partial class MainWindow : Window
-    {
-        public ObservableCollection<Item> Items { get; }
-        public MainWindow()
-        {
-            InitializeComponent();
-            DataContext = this;
-            Items = new ObservableCollection<Item>
-            {
-               new Item(),
-               new Item(),
-               new Item(),
-               new Item(),
-               new Item(),
-            };
-        }
-        private void Button_Click(object sender, RoutedEventArgs e)
-        {
-            foreach(var item in Items) item.ChangeShape();
-        }
-    }
-}
-```
-## 案２
-1段間に挟まってしまうが、`DataTemplate.Trigger`で`ControlTemplate`を切り替える。
-```xaml
-<Window
-  x:Class="Questions248125.MainWindow"
-  xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
-  xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
-  xmlns:local="clr-namespace:Questions248125"
-  Width="800"
-  Height="450">
-  <Grid>
-    <ItemsControl
-      Background="Black"
-      Foreground="White"
-      ItemsSource="{Binding Items}">
-      <ItemsControl.Resources>
-        <ControlTemplate x:Key="Line">
-          <Line
-            Name="Line"
-            Stroke="{Binding Brush}"
-            StrokeThickness="3"
-            X1="0"
-            X2="{Binding Width}"
-            Y1="0"
-            Y2="0" />
-        </ControlTemplate>
-        <ControlTemplate x:Key="Rectangle">
-          <Rectangle
-            Name="Rectangle"
-            Width="{Binding Width}"
-            Height="{Binding Height}"
-            Fill="{Binding Brush}" />
-        </ControlTemplate>
-        <ControlTemplate x:Key="Ellipse">
-          <Ellipse
-            Name="Ellipse"
-            Width="{Binding Width}"
-            Height="{Binding Height}"
-            Fill="{Binding Brush}" />
-        </ControlTemplate>
-        <DataTemplate DataType="{x:Type local:Item}">
-          <Control Name="Control" />
-          <DataTemplate.Triggers>
-            <DataTrigger Binding="{Binding ItemType}" Value="Line">
-              <DataTrigger.Setters>
-                <Setter TargetName="Control" Property="Template" Value="{StaticResource Line}" />
-              </DataTrigger.Setters>
-            </DataTrigger>
-            <DataTrigger Binding="{Binding ItemType}" Value="Rectangle">
-              <DataTrigger.Setters>
-                <Setter TargetName="Control" Property="Template" Value="{StaticResource Rectangle}" />
-              </DataTrigger.Setters>
-            </DataTrigger>
-            <DataTrigger Binding="{Binding ItemType}" Value="Ellipse">
-              <DataTrigger.Setters>
-                <Setter TargetName="Control" Property="Template" Value="{StaticResource Ellipse}" />
-              </DataTrigger.Setters>
-            </DataTrigger>
-          </DataTemplate.Triggers>
-        </DataTemplate>
-      </ItemsControl.Resources>
-      <ItemsControl.ItemsPanel>
-        <ItemsPanelTemplate>
-          <Canvas />
-        </ItemsPanelTemplate>
-      </ItemsControl.ItemsPanel>
-      <ItemsControl.ItemContainerStyle>
-        <Style>
-          <Setter Property="Canvas.Top" Value="{Binding Y}" />
-          <Setter Property="Canvas.Left" Value="{Binding X}" />
-        </Style>
-      </ItemsControl.ItemContainerStyle>
-    </ItemsControl>
-    <Button
-      HorizontalAlignment="Center"
-      VerticalAlignment="Top"
-      Click="Button_Click"
-      Content="ChangeShapes" />
-  </Grid>
-</Window>
-```
-C#コードは同じ
-## 案３
-いっそのこと`DependencyProperty`で`ItemType`を持った専用コントロールを作ってしまう。
+ちょっと要望と違うのですが、各ItemTypeごとにクラスを分けてしまえばよいのではないでしょうか？（Triggerが手強かったので諦めただけですが^^;
+文字数制限によりコード削除（編集履歴を参照）
+---
+追記
+## 案１
+バカバカしいが全パターンを入れておいて、`Visibility`で切り替え（ボツでしょうねぇ）
+```xml
+<Window
+  x:Class="Questions248125.MainWindow"
+  xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
+  xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+  xmlns:local="clr-namespace:Questions248125"
+  Width="800"
+  Height="450">
+  <Grid>
+    <ItemsControl
+      Background="Black"
+      Foreground="White"
+      ItemsSource="{Binding Items}">
+      <ItemsControl.Resources>
+        <DataTemplate DataType="{x:Type local:Item}">
+          <Grid>
+            <Line
+              Name="Line"
+              Stroke="{Binding Brush}"
+              StrokeThickness="3"
+              X1="0"
+              X2="{Binding Width}"
+              Y1="0"
+              Y2="0" />
+            <Rectangle
+              Name="Rectangle"
+              Width="{Binding Width}"
+              Height="{Binding Height}"
+              Fill="{Binding Brush}" />
+            <Ellipse
+              Name="Ellipse"
+              Width="{Binding Width}"
+              Height="{Binding Height}"
+              Fill="{Binding Brush}" />
+          </Grid>
+          <DataTemplate.Triggers>
+            <DataTrigger Binding="{Binding ItemType}" Value="Line">
+              <DataTrigger.Setters>
+                <Setter TargetName="Line" Property="Visibility" Value="Visible" />
+                <Setter TargetName="Rectangle" Property="Visibility" Value="Collapsed" />
+                <Setter TargetName="Ellipse" Property="Visibility" Value="Collapsed" />
+              </DataTrigger.Setters>
+            </DataTrigger>
+            <DataTrigger Binding="{Binding ItemType}" Value="Rectangle">
+              <DataTrigger.Setters>
+                <Setter TargetName="Line" Property="Visibility" Value="Collapsed" />
+                <Setter TargetName="Rectangle" Property="Visibility" Value="Visible" />
+                <Setter TargetName="Ellipse" Property="Visibility" Value="Collapsed" />
+              </DataTrigger.Setters>
+            </DataTrigger>
+            <DataTrigger Binding="{Binding ItemType}" Value="Ellipse">
+              <DataTrigger.Setters>
+                <Setter TargetName="Line" Property="Visibility" Value="Collapsed" />
+                <Setter TargetName="Rectangle" Property="Visibility" Value="Collapsed" />
+                <Setter TargetName="Ellipse" Property="Visibility" Value="Visible" />
+              </DataTrigger.Setters>
+            </DataTrigger>
+          </DataTemplate.Triggers>
+        </DataTemplate>
+      </ItemsControl.Resources>
+      <ItemsControl.ItemsPanel>
+        <ItemsPanelTemplate>
+          <Canvas />
+        </ItemsPanelTemplate>
+      </ItemsControl.ItemsPanel>
+      <ItemsControl.ItemContainerStyle>
+        <Style>
+          <Setter Property="Canvas.Top" Value="{Binding Y}" />
+          <Setter Property="Canvas.Left" Value="{Binding X}" />
+        </Style>
+      </ItemsControl.ItemContainerStyle>
+    </ItemsControl>
+    <Button
+      HorizontalAlignment="Center"
+      VerticalAlignment="Top"
+      Click="Button_Click"
+      Content="ChangeShapes" />
+  </Grid>
+</Window>
+```
+```cs
+using System;
+using System.Collections.ObjectModel;
+using System.ComponentModel;
+using System.Runtime.CompilerServices;
+using System.Windows;
+using System.Windows.Media;
+namespace Questions248125
+{
+    public enum ItemType { Line, Rectangle, Ellipse, }
+    public class Item : INotifyPropertyChanged
+    {
+        public int X { get; }
+        public int Y { get; }
+        public int Width { get; }
+        public int Height { get; }
+        public SolidColorBrush Brush { get; }
+        public ItemType ItemType { get => _ItemType; set => Set(ref _ItemType, value, null); }
+        public ItemType _ItemType;
+        private static readonly Random r = new Random();
+        private static readonly Array types = Enum.GetValues(typeof(ItemType));
+        public Item()
+        {
+            X = r.Next(700);
+            Y = r.Next(350);
+            Width = r.Next(400);
+            Height = r.Next(300);
+            Brush = new SolidColorBrush(Color.FromRgb((byte)r.Next(255), (byte)r.Next(255), (byte)r.Next(255)));
+            ItemType = (ItemType)types.GetValue(r.Next(types.Length));
+        }
+        public void ChangeShape() => ItemType = (ItemType)types.GetValue(r.Next(types.Length));
+        #region INotifyPropertyChanged
+        public event PropertyChangedEventHandler PropertyChanged;
+        protected bool Set<T>(ref T storage, T value, [CallerMemberName] string propertyName = null)
+        {
+            if(Equals(storage, value)) return false;
+            storage = value;
+            OnPropertyChanged(propertyName);
+            return true;
+        }
+        protected void OnPropertyChanged([CallerMemberName] string propertyName = null)
+            => PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
+        #endregion
+    }
+    public partial class MainWindow : Window
+    {
+        public ObservableCollection<Item> Items { get; }
+        public MainWindow()
+        {
+            InitializeComponent();
+            DataContext = this;
+            Items = new ObservableCollection<Item>
+            {
+               new Item(),
+               new Item(),
+               new Item(),
+               new Item(),
+               new Item(),
+            };
+        }
+        private void Button_Click(object sender, RoutedEventArgs e)
+        {
+            foreach(var item in Items) item.ChangeShape();
+        }
+    }
+}
+```
+## 案２
+1段間に挟まってしまうが、`DataTemplate.Trigger`で`ControlTemplate`を切り替える。
+```xml
+<Window
+  x:Class="Questions248125.MainWindow"
+  xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
+  xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+  xmlns:local="clr-namespace:Questions248125"
+  Width="800"
+  Height="450">
+  <Grid>
+    <ItemsControl
+      Background="Black"
+      Foreground="White"
+      ItemsSource="{Binding Items}">
+      <ItemsControl.Resources>
+        <ControlTemplate x:Key="Line">
+          <Line
+            Name="Line"
+            Stroke="{Binding Brush}"
+            StrokeThickness="3"
+            X1="0"
+            X2="{Binding Width}"
+            Y1="0"
+            Y2="0" />
+        </ControlTemplate>
+        <ControlTemplate x:Key="Rectangle">
+          <Rectangle
+            Name="Rectangle"
+            Width="{Binding Width}"
+            Height="{Binding Height}"
+            Fill="{Binding Brush}" />
+        </ControlTemplate>
+        <ControlTemplate x:Key="Ellipse">
+          <Ellipse
+            Name="Ellipse"
+            Width="{Binding Width}"
+            Height="{Binding Height}"
+            Fill="{Binding Brush}" />
+        </ControlTemplate>
+        <DataTemplate DataType="{x:Type local:Item}">
+          <Control Name="Control" />
+          <DataTemplate.Triggers>
+            <DataTrigger Binding="{Binding ItemType}" Value="Line">
+              <DataTrigger.Setters>
+                <Setter TargetName="Control" Property="Template" Value="{StaticResource Line}" />
+              </DataTrigger.Setters>
+            </DataTrigger>
+            <DataTrigger Binding="{Binding ItemType}" Value="Rectangle">
+              <DataTrigger.Setters>
+                <Setter TargetName="Control" Property="Template" Value="{StaticResource Rectangle}" />
+              </DataTrigger.Setters>
+            </DataTrigger>
+            <DataTrigger Binding="{Binding ItemType}" Value="Ellipse">
+              <DataTrigger.Setters>
+                <Setter TargetName="Control" Property="Template" Value="{StaticResource Ellipse}" />
+              </DataTrigger.Setters>
+            </DataTrigger>
+          </DataTemplate.Triggers>
+        </DataTemplate>
+      </ItemsControl.Resources>
+      <ItemsControl.ItemsPanel>
+        <ItemsPanelTemplate>
+          <Canvas />
+        </ItemsPanelTemplate>
+      </ItemsControl.ItemsPanel>
+      <ItemsControl.ItemContainerStyle>
+        <Style>
+          <Setter Property="Canvas.Top" Value="{Binding Y}" />
+          <Setter Property="Canvas.Left" Value="{Binding X}" />
+        </Style>
+      </ItemsControl.ItemContainerStyle>
+    </ItemsControl>
+    <Button
+      HorizontalAlignment="Center"
+      VerticalAlignment="Top"
+      Click="Button_Click"
+      Content="ChangeShapes" />
+  </Grid>
+</Window>
+```
+C#コードは同じ
+## 案３
+いっそのこと`DependencyProperty`で`ItemType`を持った専用コントロールを作ってしまう。
 これも方向性が違うのでコードは省略。

追記

2020/03/23 02:05

投稿

TN8001

スコア10111

answer CHANGED Viewed

@@ -1,12 +1,19 @@
-ちょっと要望と違うのですが、各`ItemType`ごとにクラスを分けてしまえばよいのではないでしょうか？（Triggerが手強かったので諦めただけですが^^;
+ちょっと要望と違うのですが、各ItemTypeごとにクラスを分けてしまえばよいのではないでしょうか？（Triggerが手強かったので諦めただけですが^^;
+文字数制限によりコード削除（編集履歴を参照）
+---
+追記
+## 案１
+バカバカしいが全パターンを入れておいて、`Visibility`で切り替え（ボツでしょうねぇ）
 ```xaml
 <Window
   x:Class="Questions248125.MainWindow"
   xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
   xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
   xmlns:local="clr-namespace:Questions248125"
-  Title="MainWindow"
   Width="800"
   Height="450">
   <Grid>
@@ -16,29 +23,52 @@
       ItemsSource="{Binding Items}">
       <ItemsControl.Resources>
-        <DataTemplate DataType="{x:Type local:Line}">
+        <DataTemplate DataType="{x:Type local:Item}">
+          <Grid>
-          <Line
+            <Line
+              Name="Line"
-            Stroke="{Binding Brush}"
+              Stroke="{Binding Brush}"
-            StrokeThickness="3"
+              StrokeThickness="3"
-            X1="0"
+              X1="0"
-            X2="{Binding Width}"
+              X2="{Binding Width}"
-            Y1="0"
+              Y1="0"
-            Y2="0" />
+              Y2="0" />
+            <Rectangle
+              Name="Rectangle"
+              Width="{Binding Width}"
+              Height="{Binding Height}"
+              Fill="{Binding Brush}" />
+            <Ellipse
+              Name="Ellipse"
+              Width="{Binding Width}"
+              Height="{Binding Height}"
+              Fill="{Binding Brush}" />
+          </Grid>
+          <DataTemplate.Triggers>
+            <DataTrigger Binding="{Binding ItemType}" Value="Line">
+              <DataTrigger.Setters>
+                <Setter TargetName="Line" Property="Visibility" Value="Visible" />
+                <Setter TargetName="Rectangle" Property="Visibility" Value="Collapsed" />
+                <Setter TargetName="Ellipse" Property="Visibility" Value="Collapsed" />
+              </DataTrigger.Setters>
+            </DataTrigger>
+            <DataTrigger Binding="{Binding ItemType}" Value="Rectangle">
+              <DataTrigger.Setters>
+                <Setter TargetName="Line" Property="Visibility" Value="Collapsed" />
+                <Setter TargetName="Rectangle" Property="Visibility" Value="Visible" />
+                <Setter TargetName="Ellipse" Property="Visibility" Value="Collapsed" />
+              </DataTrigger.Setters>
+            </DataTrigger>
+            <DataTrigger Binding="{Binding ItemType}" Value="Ellipse">
+              <DataTrigger.Setters>
+                <Setter TargetName="Line" Property="Visibility" Value="Collapsed" />
+                <Setter TargetName="Rectangle" Property="Visibility" Value="Collapsed" />
+                <Setter TargetName="Ellipse" Property="Visibility" Value="Visible" />
+              </DataTrigger.Setters>
+            </DataTrigger>
+          </DataTemplate.Triggers>
         </DataTemplate>
-        <DataTemplate DataType="{x:Type local:Rectangle}">
-          <Rectangle
-            Width="{Binding Width}"
-            Height="{Binding Height}"
-            Fill="{Binding Brush}" />
-        </DataTemplate>
-        <DataTemplate DataType="{x:Type local:Ellipse}">
-          <Ellipse
-            Width="{Binding Width}"
-            Height="{Binding Height}"
-            Fill="{Binding Brush}" />
-        </DataTemplate>
       </ItemsControl.Resources>
       <ItemsControl.ItemsPanel>
         <ItemsPanelTemplate>
@@ -54,11 +84,10 @@
     </ItemsControl>
     <Button
-      Width="80"
       HorizontalAlignment="Center"
       VerticalAlignment="Top"
       Click="Button_Click"
-      Content="Add" />
+      Content="ChangeShapes" />
   </Grid>
 </Window>
 ```
@@ -66,23 +95,28 @@
 ```C#
 using System;
 using System.Collections.ObjectModel;
+using System.ComponentModel;
+using System.Runtime.CompilerServices;
 using System.Windows;
 using System.Windows.Media;
 namespace Questions248125
 {
+    public enum ItemType { Line, Rectangle, Ellipse, }
-    public class Line : Item { }
+    public class Item : INotifyPropertyChanged
-    public class Rectangle : Item { }
-    public class Ellipse : Item { }
-    public class Item
     {
         public int X { get; }
         public int Y { get; }
         public int Width { get; }
         public int Height { get; }
         public SolidColorBrush Brush { get; }
+        public ItemType ItemType { get => _ItemType; set => Set(ref _ItemType, value, null); }
+        public ItemType _ItemType;
         private static readonly Random r = new Random();
+        private static readonly Array types = Enum.GetValues(typeof(ItemType));
         public Item()
         {
             X = r.Next(700);
@@ -90,7 +124,23 @@
             Width = r.Next(400);
             Height = r.Next(300);
             Brush = new SolidColorBrush(Color.FromRgb((byte)r.Next(255), (byte)r.Next(255), (byte)r.Next(255)));
+            ItemType = (ItemType)types.GetValue(r.Next(types.Length));
         }
+        public void ChangeShape() => ItemType = (ItemType)types.GetValue(r.Next(types.Length));
+        #region INotifyPropertyChanged
+        public event PropertyChangedEventHandler PropertyChanged;
+        protected bool Set<T>(ref T storage, T value, [CallerMemberName] string propertyName = null)
+        {
+            if(Equals(storage, value)) return false;
+            storage = value;
+            OnPropertyChanged(propertyName);
+            return true;
+        }
+        protected void OnPropertyChanged([CallerMemberName] string propertyName = null)
+            => PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
+        #endregion
     }
     public partial class MainWindow : Window
@@ -104,20 +154,106 @@
             DataContext = this;
             Items = new ObservableCollection<Item>
             {
-               new Line(),
+               new Item(),
-               new Rectangle(),
-               new Ellipse(),
+               new Item(),
+               new Item(),
+               new Item(),
+               new Item(),
             };
         }
         private void Button_Click(object sender, RoutedEventArgs e)
         {
-            switch(new Random().Next(3))
-            {
-                case 0: Items.Add(new Line()); break;
-                case 1: Items.Add(new Rectangle()); break;
+            foreach(var item in Items) item.ChangeShape();
-                case 2: Items.Add(new Ellipse()); break;
-            }
         }
     }
 }
-```
+```
+## 案２
+1段間に挟まってしまうが、`DataTemplate.Trigger`で`ControlTemplate`を切り替える。
+```xaml
+<Window
+  x:Class="Questions248125.MainWindow"
+  xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
+  xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+  xmlns:local="clr-namespace:Questions248125"
+  Width="800"
+  Height="450">
+  <Grid>
+    <ItemsControl
+      Background="Black"
+      Foreground="White"
+      ItemsSource="{Binding Items}">
+      <ItemsControl.Resources>
+        <ControlTemplate x:Key="Line">
+          <Line
+            Name="Line"
+            Stroke="{Binding Brush}"
+            StrokeThickness="3"
+            X1="0"
+            X2="{Binding Width}"
+            Y1="0"
+            Y2="0" />
+        </ControlTemplate>
+        <ControlTemplate x:Key="Rectangle">
+          <Rectangle
+            Name="Rectangle"
+            Width="{Binding Width}"
+            Height="{Binding Height}"
+            Fill="{Binding Brush}" />
+        </ControlTemplate>
+        <ControlTemplate x:Key="Ellipse">
+          <Ellipse
+            Name="Ellipse"
+            Width="{Binding Width}"
+            Height="{Binding Height}"
+            Fill="{Binding Brush}" />
+        </ControlTemplate>
+        <DataTemplate DataType="{x:Type local:Item}">
+          <Control Name="Control" />
+          <DataTemplate.Triggers>
+            <DataTrigger Binding="{Binding ItemType}" Value="Line">
+              <DataTrigger.Setters>
+                <Setter TargetName="Control" Property="Template" Value="{StaticResource Line}" />
+              </DataTrigger.Setters>
+            </DataTrigger>
+            <DataTrigger Binding="{Binding ItemType}" Value="Rectangle">
+              <DataTrigger.Setters>
+                <Setter TargetName="Control" Property="Template" Value="{StaticResource Rectangle}" />
+              </DataTrigger.Setters>
+            </DataTrigger>
+            <DataTrigger Binding="{Binding ItemType}" Value="Ellipse">
+              <DataTrigger.Setters>
+                <Setter TargetName="Control" Property="Template" Value="{StaticResource Ellipse}" />
+              </DataTrigger.Setters>
+            </DataTrigger>
+          </DataTemplate.Triggers>
+        </DataTemplate>
+      </ItemsControl.Resources>
+      <ItemsControl.ItemsPanel>
+        <ItemsPanelTemplate>
+          <Canvas />
+        </ItemsPanelTemplate>
+      </ItemsControl.ItemsPanel>
+      <ItemsControl.ItemContainerStyle>
+        <Style>
+          <Setter Property="Canvas.Top" Value="{Binding Y}" />
+          <Setter Property="Canvas.Left" Value="{Binding X}" />
+        </Style>
+      </ItemsControl.ItemContainerStyle>
+    </ItemsControl>
+    <Button
+      HorizontalAlignment="Center"
+      VerticalAlignment="Top"
+      Click="Button_Click"
+      Content="ChangeShapes" />
+  </Grid>
+</Window>
+```
+C#コードは同じ
+## 案３
+いっそのこと`DependencyProperty`で`ItemType`を持った専用コントロールを作ってしまう。
+これも方向性が違うのでコードは省略。