Neue Funktion Schüler austragen statt aus Kurs löschen.

LehrerApp.Desktop/Views/Groups/GroupDetailView.axaml

@@ -20,9 +20,14 @@
             <Run Text="{Binding StudentCount}"/>
             <Run Text=" Schüler"/>
           </TextBlock>
+          <CheckBox Content="Ausgetretene anzeigen" IsChecked="{Binding ShowFormerStudents}"
+                    VerticalAlignment="Center"/>
           <Button Content="＋ Schüler"   Command="{Binding AddStudentCommand}"/>
-          <Button Content="− Austragen"  Command="{Binding RemoveStudentCommand}"
+          <Button Content="{Binding SelectedStudent.WithdrawActionLabel}"
+                  Command="{Binding WithdrawStudentCommand}"
                   IsVisible="{Binding SelectedStudent, Converter={x:Static ObjectConverters.IsNotNull}}"/>
+          <Button Content="Austragung zurücknehmen" Command="{Binding ReinstateStudentCommand}"
+                  IsVisible="{Binding SelectedStudent.HasExitDate}"/>
           <Button Content="＋ Klausur"   Command="{Binding AddExamCommand}"/>
         </StackPanel>
       </Grid>
@@ -52,8 +57,9 @@
                   CanUserResizeColumns="True"
                   Margin="0">
           <DataGrid.Columns>
-            <DataGridTextColumn Header="Name"    Binding="{Binding FullName}"    Width="*"/>
-            <DataGridTextColumn Header="Zeitraum" Binding="{Binding PeriodLabel}" Width="90"/>
+            <DataGridTextColumn Header="Name"     Binding="{Binding FullName}"         Width="*"/>
+            <DataGridTextColumn Header="Zeitraum" Binding="{Binding PeriodLabel}"      Width="190"/>
+            <DataGridTextColumn Header="Status"   Binding="{Binding MembershipStatus}" Width="170"/>
             <DataGridTemplateColumn Header="Niveau" Width="130"
                                      IsVisible="{Binding IsDifferentiated}">
               <DataGridTemplateColumn.CellTemplate>