回答編集履歴

  `TextBlock`は軽量コンポーネントとして`FrameworkElement`派生なので、`Template`等がなくあんまり凝ったことはできないです。

 

  今の解釈でこういうことかな？？というサンプルを作りました。

  `Canvas`ベースなのも特別意味はありません。

 

  添付ビヘイビアはいろいろとガバガバなので、このままでは使い物にならないだろうと思います。

 

  <Window

  x:Class="Questions264652.MainWindow"

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

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

  xmlns:local="clr-namespace:Questions264652"

  Width="800"

  Height="450">

  <Grid>

  <Grid.RowDefinitions>

  <RowDefinition />

  <RowDefinition />

  </Grid.RowDefinitions>

  <Grid.ColumnDefinitions>

  <ColumnDefinition />

  <ColumnDefinition />

  </Grid.ColumnDefinitions>

  <GroupBox Header="今の状態">

  Canvas.Left="35"

  Canvas.Top="24"

  Text="ほげほげ" />

  Canvas.Left="177"

  Canvas.Top="49"

  Text="ふがふが" />

 

  <GroupBox Grid.Column="1" Header="こうなるといいなの状態">

  <TextBlock Canvas.Left="35" Canvas.Top="24">

  <InlineUIContainer BaselineAlignment="Center">

  <Image Width="20" Source="https://teratail-v2.storage.googleapis.com/uploads/avatars/u13/132786/KnkDDC5A_thumbnail_32x32.jpg" />

  </InlineUIContainer>

  <Run>ほげほげ</Run>

  <Bold>!!</Bold>

  </TextBlock>

  <TextBlock Canvas.Left="177" Canvas.Top="49">

  <InlineUIContainer BaselineAlignment="Center">

  <Image Width="20" Source="https://teratail-v2.storage.googleapis.com/uploads/avatars/u13/132786/KnkDDC5A_thumbnail_32x32.jpg" />

  </InlineUIContainer>

  <Run>ふがふが</Run>

  <Bold>!!</Bold>

  </TextBlock>

 

  <GroupBox Grid.Row="1" Header="テンブレート">

  <Canvas.Resources>

  <Style TargetType="ContentControl">

  <Setter Property="Template">

  <Setter.Value>

  <ControlTemplate TargetType="ContentControl">

  <TextBlock>

  <InlineUIContainer BaselineAlignment="Center">

  <Image Width="20" Source="https://teratail-v2.storage.googleapis.com/uploads/avatars/u13/132786/KnkDDC5A_thumbnail_32x32.jpg" />

  </InlineUIContainer>

  <Run Text="{TemplateBinding Content}" />

  <Bold>!!</Bold>

  </TextBlock>

  </ControlTemplate>

  </Setter.Value>

  </Setter>

  </Style>

  </Canvas.Resources>

  <ContentControl

  Canvas.Left="35"

  Canvas.Top="24"

  Content="ほげほげ" />

  <ContentControl

  Canvas.Left="177"

  Canvas.Top="49"

  Content="ふがふが" />

 

  <GroupBox

  Grid.Row="1"

  Grid.Column="1"

  Header="添付ビヘイビア">

  <Canvas.Resources>

  <InlineUIContainer

  x:Key="image"

  x:Shared="False"

  BaselineAlignment="Center">

  <Image Width="20" Source="https://teratail-v2.storage.googleapis.com/uploads/avatars/u13/132786/KnkDDC5A_thumbnail_32x32.jpg" />

  </InlineUIContainer>

  <Bold x:Key="exclamation" x:Shared="False">!!</Bold>

 

  <Style TargetType="TextBlock">

  <Setter Property="local:AddInlineBehavior.Before" Value="{StaticResource image}" />

  <Setter Property="local:AddInlineBehavior.After" Value="{StaticResource exclamation}" />

  <Setter Property="local:AddInlineBehavior.Use" Value="True" />

  </Style>

  </Canvas.Resources>

 

  Canvas.Left="35"

  Canvas.Top="24"

  Text="ほげほげ" />

  Canvas.Left="177"

  Canvas.Top="49"

  Text="ふがふが" />

  </Grid>

  </Window>

  ```

 

  using System.Windows;

  using System.Windows.Controls;

  using System.Windows.Documents;

 

  namespace Questions264652

  {

  public class AddInlineBehavior

  {

  public static DependencyProperty UseProperty

  = DependencyProperty.RegisterAttached("Use", typeof(bool), typeof(AddInlineBehavior),

  new PropertyMetadata(false, OnUseChanged));

  public static void SetUse(DependencyObject obj, bool value) => obj.SetValue(UseProperty, value);

  public static bool GetUse(DependencyObject obj) => (bool)obj.GetValue(UseProperty);

  private static void OnUseChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)

  {

  if(d is TextBlock textBlock)

  {

  if((bool)e.NewValue)

  {

  var tmp = textBlock.Text;

  textBlock.Inlines.Clear();

  if(GetBefore(textBlock) is Inline before)

  {

  textBlock.Inlines.Add(before);

  textBlock.Inlines.Add(new Run(" "));

  }

  textBlock.Inlines.Add(new Run(tmp));

  if(GetAfter(textBlock) is Inline after)

  {

  textBlock.Inlines.Add(new Run(" "));

  textBlock.Inlines.Add(after);

  }

  }

  }

  }

 

  public static DependencyProperty BeforeProperty

  = DependencyProperty.RegisterAttached("Before", typeof(Inline), typeof(AddInlineBehavior),

  new PropertyMetadata(null));

  public static void SetBefore(DependencyObject obj, Inline value) => obj.SetValue(BeforeProperty, value);

  public static Inline GetBefore(DependencyObject obj) => (Inline)obj.GetValue(BeforeProperty);

 

  public static DependencyProperty AfterProperty

  = DependencyProperty.RegisterAttached("After", typeof(Inline), typeof(AddInlineBehavior),

  new PropertyMetadata(null));

  public static void SetAfter(DependencyObject obj, Inline value) => obj.SetValue(AfterProperty, value);

  public static Inline GetAfter(DependencyObject obj) => (Inline)obj.GetValue(AfterProperty);

  }

  }

  ```