LehrerApp/LehrerApp.Desktop/Views/Groups/ParticipationTabView.axaml

<UserControl xmlns="https://github.com/avaloniaui"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:vm="clr-namespace:LehrerApp.Desktop.ViewModels.Groups"
             x:Class="LehrerApp.Desktop.Views.Groups.ParticipationTabView"
             x:DataType="vm:ParticipationTabViewModel">

  <Grid ColumnDefinitions="220,*">

    <!-- Linke Seite: Sitzungsliste -->
    <Border Grid.Column="0"
            BorderBrush="{DynamicResource SystemControlForegroundBaseLowBrush}"
            BorderThickness="0,0,1,0">
    <Grid RowDefinitions="Auto,Auto,*">

      <StackPanel Grid.Row="0" Orientation="Horizontal" Spacing="6" Margin="10,10,10,6">
        <Button Content="＋ Sitzung" Command="{Binding AddSessionCommand}" HorizontalAlignment="Stretch"/>
        <Button Content="Schnell" Command="{Binding QuickInputCommand}"/>
      </StackPanel>

      <Button Grid.Row="1" Content="Ø Mitarbeitsnote" Command="{Binding ComputeGradeCommand}"
              HorizontalAlignment="Stretch" Margin="10,0,10,6"/>

      <ListBox Grid.Row="2"
               ItemsSource="{Binding Sessions}"
               SelectedItem="{Binding SelectedSession}"
               BorderThickness="0">
        <ListBox.ItemTemplate>
          <DataTemplate x:DataType="vm:ParticipationSessionItem">
            <TextBlock Text="{Binding Display}" TextWrapping="Wrap" Padding="4,3" FontSize="12"/>
          </DataTemplate>
        </ListBox.ItemTemplate>
      </ListBox>
    </Grid>
    </Border>

    <!-- Rechte Seite -->
    <Grid Grid.Column="1" RowDefinitions="Auto,Auto,*">

      <!-- Header: Session-Titel + Toggle-Buttons -->
      <Grid Grid.Row="0" ColumnDefinitions="*,Auto" Margin="12,8,12,4"
            IsVisible="{Binding SelectedSession, Converter={x:Static ObjectConverters.IsNotNull}}">
        <TextBlock Grid.Column="0"
                   Text="{Binding SelectedSessionDisplay}"
                   FontSize="13" FontWeight="SemiBold"
                   VerticalAlignment="Center"/>
        <StackPanel Grid.Column="1" Orientation="Horizontal" Spacing="6"
                    IsVisible="{Binding HasCompetencyCatalog}">
          <ToggleButton Content="◇ Kompetenzen"
                        IsChecked="{Binding CompetencyTagsVisible}"
                        FontSize="11" Padding="8,3"/>
          <ToggleButton Content="◈ Schüler-Ratings"
                        IsChecked="{Binding StudentCompetencyRatingsVisible}"
                        FontSize="11" Padding="8,3"/>
        </StackPanel>
      </Grid>

      <!-- Kompetenz-Tag-Panel -->
      <Border Grid.Row="1"
              IsVisible="{Binding CompetencyTagsVisible}"
              BorderBrush="{DynamicResource SystemControlForegroundBaseLowBrush}"
              BorderThickness="0,0,0,1"
              Padding="12,8">
        <ScrollViewer HorizontalScrollBarVisibility="Disabled" MaxHeight="200">
          <ItemsControl ItemsSource="{Binding CompetencyTagGroups}">
            <ItemsControl.ItemTemplate>
              <DataTemplate DataType="vm:CompetencyTagGroup">
                <StackPanel Spacing="4" Margin="0,0,0,10">
                  <TextBlock Text="{Binding DisplayName}"
                             FontSize="11" FontWeight="SemiBold" Opacity="0.55"/>
                  <ItemsControl ItemsSource="{Binding Items}">
                    <ItemsControl.ItemsPanel>
                      <ItemsPanelTemplate>
                        <WrapPanel Orientation="Horizontal"/>
                      </ItemsPanelTemplate>
                    </ItemsControl.ItemsPanel>
                    <ItemsControl.ItemTemplate>
                      <DataTemplate DataType="vm:CompetencyTag">
                        <ToggleButton IsChecked="{Binding IsSelected}"
                                      Content="{Binding Display}"
                                      FontSize="11"
                                      Padding="6,3"
                                      Margin="0,0,4,4"/>
                      </DataTemplate>
                    </ItemsControl.ItemTemplate>
                  </ItemsControl>
                </StackPanel>
              </DataTemplate>
            </ItemsControl.ItemTemplate>
          </ItemsControl>
        </ScrollViewer>
      </Border>

      <!-- DataGrid: Spalten werden in ParticipationTabView.axaml.cs dynamisch erzeugt -->
      <DataGrid Grid.Row="2"
                x:Name="RatingGrid"
                ItemsSource="{Binding StudentRows}"
                AutoGenerateColumns="False"
                IsReadOnly="True"
                GridLinesVisibility="All"
                CanUserReorderColumns="False"
                CanUserResizeColumns="True"
                IsVisible="{Binding SelectedSession, Converter={x:Static ObjectConverters.IsNotNull}}"/>

      <TextBlock Grid.Row="2"
                 Text="{Binding NoDataText}"
                 HorizontalAlignment="Center" VerticalAlignment="Center"
                 Opacity="0.35" FontSize="14"
                 IsVisible="{Binding SelectedSession, Converter={x:Static ObjectConverters.IsNull}}"/>
    </Grid>
  </Grid>
</UserControl>