Klausur: Fach aus Lerngruppe übernehmen, Rückgabedatum erfassen

- Fach kommt jetzt aus der Lerngruppe statt manuell pro Klausur
  eingegeben zu werden: Fach-Feld im Anlegen-Dialog der Lerngruppe
  ist nicht mehr auf Typ "Kurs" beschränkt, da eine Gruppe genau ein
  Fach unterrichtet (bei zwei Fächern legt man zwei Gruppen an). Im
  Klausur-Dialog ist das Fach dadurch nur noch read-only Kontext statt
  eines redundanten Eingabefelds.
- Neues Feld Exam.ReturnedAt: wird beim Statuswechsel auf "Zurück-
  gegeben" automatisch mit dem heutigen Datum belegt (und beim
  Zurücknehmen des Status wieder geleert), ist im Klausur-Dialog aber
  auch manuell nachträglich korrigierbar. Sichtbar als eigene Spalte
  im Klausuren-Tab.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

LehrerApp.Core/Models/Exam.cs

@@ -11,6 +11,7 @@ public class Exam
     public List<ExamTask> Tasks { get; set; } = [];
     public List<GradingKeyEntry> GradingKey { get; set; } = [];
     public ExamStatus Status { get; set; } = ExamStatus.Planned;
+    public DateOnly? ReturnedAt { get; set; }
     public string? Notes { get; set; }
     public DateTime CreatedAt { get; set; } = DateTime.UtcNow;
     public DateTime UpdatedAt { get; set; } = DateTime.UtcNow;
@@ -21,6 +22,7 @@ public class ExamTask
     public string? Title { get; set; }
     public double MaxPoints { get; set; }
     public double Weight { get; set; } = 1.0;
+    public List<string> CompetencyCodes { get; set; } = [];
 }
 public class GradingKeyEntry
 {

LehrerApp.Data/Repositories/AllRepositories.cs

@@ -89,7 +89,12 @@ public class ExamRepository(LiteDbContext db) : IExamRepository
     public List<Exam> GetByGroup(Guid groupId) =>
         db.Exams.Find(e => e.GroupId == groupId).OrderByDescending(e => e.Date).ToList();
     public void Save(Exam e) { e.UpdatedAt = DateTime.UtcNow; db.Exams.Upsert(e); }
-    public void Delete(Guid id) => db.Exams.Delete(id);
+    public void Delete(Guid id)
+    {
+        foreach (var result in db.ExamResults.Find(r => r.ExamId == id).ToList())
+            db.ExamResults.Delete(result.Id);
+        db.Exams.Delete(id);
+    }
 }
 
 public class ExamResultRepository(LiteDbContext db) : IExamResultRepository

LehrerApp.Desktop/ViewModels/Groups/ExamViewModels.cs

@@ -0,0 +1,256 @@
+using CommunityToolkit.Mvvm.ComponentModel;
+using CommunityToolkit.Mvvm.Input;
+using LehrerApp.Core.Interfaces;
+using LehrerApp.Core.Models;
+using LehrerApp.Core.Services;
+using System.Collections.ObjectModel;
+using System.Globalization;
+
+namespace LehrerApp.Desktop.ViewModels.Groups;
+
+// ── Dialog: Klausur anlegen / bearbeiten / duplizieren ───────────────────────
+
+public partial class ExamDialogViewModel : ObservableObject
+{
+    private readonly IExamRepository _exams;
+    private readonly ICompetencyDomainRepository _competencyDomains;
+    private readonly Guid _groupId;
+    private readonly Guid? _subjectId;
+    private readonly int _gradeLevel;
+    private readonly Exam? _editingExam;
+    private readonly List<GradingKeyEntry> _gradingKey;
+    private readonly string _subjectName;
+
+    [ObservableProperty] private string _title = "";
+    [ObservableProperty] private string _dateText = DateOnly.FromDateTime(DateTime.Today).ToString("dd.MM.yyyy");
+    [ObservableProperty] private int? _examNumber;
+    [ObservableProperty] private string _notes = "";
+    [ObservableProperty] private string _returnedAtText = "";
+    [ObservableProperty] private string _validationMessage = "";
+    [ObservableProperty] private double _totalPoints;
+    [ObservableProperty] private bool _hasCompetencyCatalog;
+    [ObservableProperty] private bool _useWeighting;
+
+    public bool TotalPointsWarning => TotalPoints <= 0;
+    public string TotalPointsDisplay =>
+        $"{TotalPoints.ToString("0.##", CultureInfo.InvariantCulture)} Punkte gesamt";
+
+    public ObservableCollection<ExamTaskEditItem> Tasks { get; } = [];
+
+    public Exam? Result { get; private set; }
+    public string DialogTitle => _editingExam is null ? "Neue Klausur anlegen" : "Klausur bearbeiten";
+    public string SaveButtonText => _editingExam is null ? "Anlegen" : "Speichern";
+
+    /// Fach kommt von der Lerngruppe, nicht editierbar (jede Gruppe unterrichtet ein Fach).
+    public string SubjectDisplay => string.IsNullOrWhiteSpace(_subjectName)
+        ? "Kein Fach hinterlegt (siehe Lerngruppe)" : $"Fach: {_subjectName}";
+
+    public ExamDialogViewModel(IExamRepository exams, ICompetencyDomainRepository competencyDomains,
+        Guid groupId, Guid? subjectId, int gradeLevel, GradingSystem gradingSystem,
+        string defaultSubjectName, Exam? editingExam, Exam? duplicateSource)
+    {
+        _exams = exams; _competencyDomains = competencyDomains;
+        _groupId = groupId; _subjectId = subjectId; _gradeLevel = gradeLevel;
+        _editingExam = editingExam;
+        _subjectName = defaultSubjectName;
+
+        HasCompetencyCatalog = subjectId.HasValue
+            && _competencyDomains.GetBySubjectAndGrade(subjectId.Value, gradeLevel).Count > 0;
+
+        var source = editingExam ?? duplicateSource;
+        if (source is not null)
+        {
+            var isDuplicate = duplicateSource is not null;
+            Title      = isDuplicate ? $"{source.Title} (Kopie)" : source.Title;
+            DateText   = isDuplicate
+                ? DateOnly.FromDateTime(DateTime.Today).ToString("dd.MM.yyyy")
+                : source.Date.ToString("dd.MM.yyyy");
+            ExamNumber = source.ExamNumber;
+            Notes      = source.Notes ?? "";
+            ReturnedAtText = isDuplicate ? "" : source.ReturnedAt?.ToString("dd.MM.yyyy") ?? "";
+            _gradingKey = source.GradingKey
+                .Select(k => new GradingKeyEntry { Grade = k.Grade, MinPercent = k.MinPercent }).ToList();
+            foreach (var t in source.Tasks.OrderBy(t => t.Nr))
+                AddTaskInternal(t.Title, t.MaxPoints, t.Weight, [.. t.CompetencyCodes]);
+            UseWeighting = Tasks.Any(t => Math.Abs(t.Weight - 1.0) > 0.0001);
+        }
+        else
+        {
+            _gradingKey = gradingSystem == GradingSystem.Grades1To6
+                ? GradingService.DefaultKey1To6() : GradingService.DefaultKey0To15();
+        }
+        foreach (var t in Tasks) t.ShowWeight = UseWeighting;
+        RecomputeTotals();
+    }
+
+    partial void OnUseWeightingChanged(bool value)
+    {
+        foreach (var t in Tasks) t.ShowWeight = value;
+    }
+
+    [RelayCommand]
+    private void AddTask()
+    {
+        AddTaskInternal(null, 0, 1.0, []);
+        Tasks[^1].ShowWeight = UseWeighting;
+        RecomputeTotals();
+    }
+
+    private void AddTaskInternal(string? title, double maxPoints, double weight, List<string> competencyCodes)
+    {
+        var item = new ExamTaskEditItem(title, maxPoints, weight, competencyCodes,
+            BuildCompetencyTagGroups(competencyCodes))
+        {
+            OnChanged  = RecomputeTotals,
+            OnRemove   = RemoveTask,
+            OnMoveUp   = MoveTaskUp,
+            OnMoveDown = MoveTaskDown,
+        };
+        Tasks.Add(item);
+        RenumberTasks();
+    }
+
+    private List<CompetencyTagGroup> BuildCompetencyTagGroups(List<string> selectedCodes)
+    {
+        var groups = new List<CompetencyTagGroup>();
+        if (!_subjectId.HasValue) return groups;
+        var selected = selectedCodes.ToHashSet();
+        foreach (var domain in _competencyDomains.GetBySubjectAndGrade(_subjectId.Value, _gradeLevel))
+        {
+            var group = new CompetencyTagGroup(domain.Name, domain.Code);
+            foreach (var item in domain.Items.OrderBy(i => i.SortOrder))
+                group.Items.Add(new CompetencyTag(item.Code, item.Description, selected.Contains(item.Code)));
+            if (group.Items.Count > 0) groups.Add(group);
+        }
+        return groups;
+    }
+
+    private void RemoveTask(ExamTaskEditItem item)
+    {
+        Tasks.Remove(item);
+        RenumberTasks();
+        RecomputeTotals();
+    }
+
+    private void MoveTaskUp(ExamTaskEditItem item)
+    {
+        var idx = Tasks.IndexOf(item);
+        if (idx <= 0) return;
+        Tasks.Move(idx, idx - 1);
+        RenumberTasks();
+    }
+
+    private void MoveTaskDown(ExamTaskEditItem item)
+    {
+        var idx = Tasks.IndexOf(item);
+        if (idx < 0 || idx >= Tasks.Count - 1) return;
+        Tasks.Move(idx, idx + 1);
+        RenumberTasks();
+    }
+
+    private void RenumberTasks()
+    {
+        for (var i = 0; i < Tasks.Count; i++) Tasks[i].Nr = i + 1;
+    }
+
+    private void RecomputeTotals()
+    {
+        TotalPoints = Tasks.Sum(t => t.MaxPoints);
+        OnPropertyChanged(nameof(TotalPointsWarning));
+        OnPropertyChanged(nameof(TotalPointsDisplay));
+    }
+
+    [RelayCommand]
+    private void Save()
+    {
+        if (string.IsNullOrWhiteSpace(Title)) { ValidationMessage = "Titel erforderlich."; return; }
+        if (!DateOnly.TryParseExact(DateText, "dd.MM.yyyy", null, DateTimeStyles.None, out var date))
+        {
+            ValidationMessage = "Datum im Format TT.MM.JJJJ eingeben.";
+            return;
+        }
+        DateOnly? returnedAt = null;
+        if (!string.IsNullOrWhiteSpace(ReturnedAtText))
+        {
+            if (!DateOnly.TryParseExact(ReturnedAtText, "dd.MM.yyyy", null, DateTimeStyles.None, out var r))
+            {
+                ValidationMessage = "Rückgabedatum im Format TT.MM.JJJJ eingeben.";
+                return;
+            }
+            returnedAt = r;
+        }
+
+        Result = _editingExam ?? new Exam { GroupId = _groupId };
+        Result.Title      = Title.Trim();
+        Result.Date       = date;
+        Result.Subject    = _subjectName.Trim();
+        Result.ExamNumber = ExamNumber;
+        Result.Notes      = string.IsNullOrWhiteSpace(Notes) ? null : Notes.Trim();
+        Result.ReturnedAt = returnedAt;
+        Result.Tasks      = Tasks.Select(t => t.ToModel()).ToList();
+        Result.GradingKey = _gradingKey;
+        _exams.Save(Result);
+    }
+}
+
+// ── Zeile im Aufgaben-Editor (1.2.1 / 1.2.2 / 1.2.4) ─────────────────────────
+
+public partial class ExamTaskEditItem : ObservableObject
+{
+    [ObservableProperty] private int _nr;
+    [ObservableProperty] private string _title = "";
+    [ObservableProperty] private double _maxPoints;
+    [ObservableProperty] private double _weight = 1.0;
+    [ObservableProperty] private bool _isCompetencyPanelOpen;
+    [ObservableProperty] private bool _showWeight;
+
+    public List<string> CompetencyCodes { get; }
+    public ObservableCollection<CompetencyTagGroup> CompetencyTagGroups { get; } = [];
+
+    public string CompetencySummary => CompetencyCodes.Count == 0
+        ? "Keine Kompetenzen"
+        : $"{CompetencyCodes.Count} Kompetenz(en)";
+
+    public Action? OnChanged { get; set; }
+    public Action<ExamTaskEditItem>? OnRemove   { get; set; }
+    public Action<ExamTaskEditItem>? OnMoveUp   { get; set; }
+    public Action<ExamTaskEditItem>? OnMoveDown { get; set; }
+
+    public ExamTaskEditItem(string? title, double maxPoints, double weight,
+        List<string> competencyCodes, List<CompetencyTagGroup> tagGroups)
+    {
+        _title     = title ?? "";
+        _maxPoints = maxPoints;
+        _weight    = weight;
+        CompetencyCodes = competencyCodes;
+        foreach (var g in tagGroups)
+        {
+            foreach (var tag in g.Items) tag.OnChanged = OnCompetencyToggled;
+            CompetencyTagGroups.Add(g);
+        }
+    }
+
+    private void OnCompetencyToggled(string code, bool selected)
+    {
+        if (selected) { if (!CompetencyCodes.Contains(code)) CompetencyCodes.Add(code); }
+        else            CompetencyCodes.Remove(code);
+        OnPropertyChanged(nameof(CompetencySummary));
+        OnChanged?.Invoke();
+    }
+
+    [RelayCommand] private void ToggleCompetencyPanel() => IsCompetencyPanelOpen = !IsCompetencyPanelOpen;
+    [RelayCommand] private void Remove()   => OnRemove?.Invoke(this);
+    [RelayCommand] private void MoveUp()   => OnMoveUp?.Invoke(this);
+    [RelayCommand] private void MoveDown() => OnMoveDown?.Invoke(this);
+
+    partial void OnMaxPointsChanged(double value) => OnChanged?.Invoke();
+
+    public ExamTask ToModel() => new()
+    {
+        Nr = Nr,
+        Title = string.IsNullOrWhiteSpace(Title) ? null : Title.Trim(),
+        MaxPoints = MaxPoints,
+        Weight = Weight,
+        CompetencyCodes = CompetencyCodes,
+    };
+}

LehrerApp.Desktop/ViewModels/Groups/GroupViewModels.cs

@@ -165,12 +165,17 @@ public partial class GroupDetailViewModel : ObservableObject
     [ObservableProperty] private int _studentCount;
     [ObservableProperty] private int _activeTabIndex = 0;
     [ObservableProperty] private StudentSummary? _selectedStudent;
+    [ObservableProperty] private ExamSummary? _selectedExam;
 
     public ObservableCollection<StudentSummary> Students { get; } = [];
     public ObservableCollection<ExamSummary> Exams { get; } = [];
 
     public ParticipationTabViewModel ParticipationTab { get; }
     public Func<Task<bool>>? OnAddStudent { get; set; }
+    public Func<Guid, Task<bool>>? OnAddExam { get; set; }
+    public Func<Exam, Task<bool>>? OnEditExam { get; set; }
+    public Func<Exam, Task<bool>>? OnDuplicateExam { get; set; }
+    public Func<ExamSummary, Task<bool>>? OnConfirmDeleteExam { get; set; }
 
     public GroupDetailViewModel(IGroupRepository groups, IStudentRepository students,
         IEnrollmentRepository enrollments, IExamRepository exams, IGradeRepository grades,
@@ -190,9 +195,17 @@ public partial class GroupDetailViewModel : ObservableObject
                         $"{(Group.Type == GroupType.Class ? "Klasse" : "Kurs")} · " +
                         $"Stufe {Group.GradeLevel} · Noten {(Group.GradingSystem == GradingSystem.Grades1To6 ? "1–6" : "0–15")}";
         LoadStudents();
+        ReloadExams();
+        ParticipationTab.Initialize(Group.Id, Group.SchoolYear);
+    }
+
+    private void ReloadExams()
+    {
+        if (Group is null) return;
+        var selectedId = SelectedExam?.Id;
         Exams.Clear();
         foreach (var e in _exams.GetByGroup(Group.Id)) Exams.Add(new ExamSummary(e));
-        ParticipationTab.Initialize(Group.Id, Group.SchoolYear);
+        SelectedExam = Exams.FirstOrDefault(e => e.Id == selectedId);
     }
 
     public void LoadStudents()
@@ -240,7 +253,91 @@ public partial class GroupDetailViewModel : ObservableObject
 
     private bool HasSelectedStudent() => SelectedStudent is not null;
 
-    [RelayCommand] private void AddExam()  { /* TODO */ }
+    [RelayCommand]
+    private async Task AddExam()
+    {
+        if (Group is null || OnAddExam is null) return;
+        var saved = await OnAddExam(Group.Id);
+        if (saved) ReloadExams();
+    }
+
+    [RelayCommand(CanExecute = nameof(HasSelectedExam))]
+    private async Task EditExam()
+    {
+        if (SelectedExam is null || OnEditExam is null) return;
+        var exam = _exams.GetById(SelectedExam.Id);
+        if (exam is null) return;
+        var id = exam.Id;
+        var saved = await OnEditExam(exam);
+        if (saved)
+        {
+            ReloadExams();
+            SelectedExam = Exams.FirstOrDefault(e => e.Id == id);
+        }
+    }
+
+    [RelayCommand(CanExecute = nameof(HasSelectedExam))]
+    private async Task DuplicateExam()
+    {
+        if (SelectedExam is null || OnDuplicateExam is null) return;
+        var exam = _exams.GetById(SelectedExam.Id);
+        if (exam is null) return;
+        var saved = await OnDuplicateExam(exam);
+        if (saved) ReloadExams();
+    }
+
+    [RelayCommand(CanExecute = nameof(HasSelectedExam))]
+    private async Task DeleteExam()
+    {
+        if (SelectedExam is null || OnConfirmDeleteExam is null) return;
+        var selected = SelectedExam;
+        if (!await OnConfirmDeleteExam(selected)) return;
+        _exams.Delete(selected.Id);
+        SelectedExam = null;
+        ReloadExams();
+    }
+
+    [RelayCommand(CanExecute = nameof(HasSelectedExam))]
+    private void AdvanceExamStatus()
+    {
+        if (SelectedExam is null) return;
+        SetExamStatus(SelectedExam.Status switch
+        {
+            ExamStatus.Planned   => ExamStatus.Conducted,
+            ExamStatus.Conducted => ExamStatus.Graded,
+            ExamStatus.Graded    => ExamStatus.Returned,
+            _                    => SelectedExam.Status,
+        });
+    }
+
+    [RelayCommand(CanExecute = nameof(HasSelectedExam))]
+    private void SetExamStatus(ExamStatus status)
+    {
+        if (SelectedExam is null) return;
+        var exam = _exams.GetById(SelectedExam.Id);
+        if (exam is null) return;
+        exam.Status = status;
+        if (status == ExamStatus.Returned)
+            exam.ReturnedAt ??= DateOnly.FromDateTime(DateTime.Today);
+        else
+            exam.ReturnedAt = null;
+        _exams.Save(exam);
+        var id = exam.Id;
+        ReloadExams();
+        SelectedExam = Exams.FirstOrDefault(e => e.Id == id);
+    }
+
+    partial void OnSelectedExamChanged(ExamSummary? value)
+    {
+        EditExamCommand.NotifyCanExecuteChanged();
+        DuplicateExamCommand.NotifyCanExecuteChanged();
+        DeleteExamCommand.NotifyCanExecuteChanged();
+        AdvanceExamStatusCommand.NotifyCanExecuteChanged();
+        SetExamStatusCommand.NotifyCanExecuteChanged();
+    }
+
+    private bool HasSelectedExam() => SelectedExam is not null;
+
     [RelayCommand] private void Refresh()  { if (Group is not null) LoadGroup(Group.Id); }
 }
 
@@ -277,10 +374,15 @@ public class ExamSummary
     public Guid Id { get; }
     public string Title { get; }
     public string Date { get; }
+    public ExamStatus Status { get; }
     public string StatusLabel { get; }
+    public string StatusColorHex { get; }
+    public string ReturnedAtDisplay { get; }
+
     public ExamSummary(Core.Models.Exam e)
     {
-        Id = e.Id; Title = e.Title; Date = e.Date.ToString("dd.MM.yyyy");
+        Id = e.Id; Title = e.Title; Date = e.Date.ToString("dd.MM.yyyy"); Status = e.Status;
+        ReturnedAtDisplay = e.ReturnedAt?.ToString("dd.MM.yyyy") ?? "";
         StatusLabel = e.Status switch
         {
             ExamStatus.Planned   => "Geplant",
@@ -289,6 +391,14 @@ public class ExamSummary
             ExamStatus.Returned  => "Zurückgegeben",
             _ => "",
         };
+        StatusColorHex = e.Status switch
+        {
+            ExamStatus.Planned   => "#9E9E9E",
+            ExamStatus.Conducted => "#FB8C00",
+            ExamStatus.Graded    => "#43A047",
+            ExamStatus.Returned  => "#1E88E5",
+            _ => "#9E9E9E",
+        };
     }
 }
 
@@ -465,7 +575,7 @@ public partial class AddGroupDialogViewModel : ObservableObject
         if (string.IsNullOrWhiteSpace(Name)) { ValidationMessage = "Bezeichnung erforderlich."; return; }
         if (GradeLevel is < 1 or > 13)       { ValidationMessage = "Klassenstufe 1–13."; return; }
 
-        string? subjectName = IsKurs && !string.IsNullOrWhiteSpace(Subject) ? Subject.Trim() : null;
+        string? subjectName = !string.IsNullOrWhiteSpace(Subject) ? Subject.Trim() : null;
         Guid?   subjectId   = null;
 
         if (subjectName is not null)

LehrerApp.Desktop/Views/Groups/AddGroupDialog.axaml

@@ -25,8 +25,9 @@
         <TextBox Text="{Binding Name}" PlaceholderText="{Binding NameHint}"/>
       </StackPanel>
 
-      <!-- Fach – nur bei Kurs, AutoComplete aus bekannten Fächern -->
-      <StackPanel Spacing="4" IsVisible="{Binding IsKurs}">
+      <!-- Fach – AutoComplete aus bekannten Fächern; auch bei Klasse, da eine
+           Lerngruppe genau ein Fach unterrichtet (bei zwei Fächern: zwei Gruppen anlegen) -->
+      <StackPanel Spacing="4">
         <TextBlock Text="Fach (optional)" FontSize="12" Opacity="0.7"/>
         <AutoCompleteBox Text="{Binding Subject}"
                          ItemsSource="{Binding KnownSubjectNames}"

LehrerApp.Desktop/Views/Groups/DeleteExamDialog.axaml

@@ -0,0 +1,20 @@
+<Window xmlns="https://github.com/avaloniaui"
+        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+        x:Class="LehrerApp.Desktop.Views.Groups.DeleteExamDialog"
+        x:CompileBindings="False"
+        Title="Klausur löschen"
+        Width="430" SizeToContent="Height"
+        CanResize="False" WindowStartupLocation="CenterOwner">
+  <Grid RowDefinitions="*,Auto" Margin="24">
+    <StackPanel Grid.Row="0" Spacing="12">
+      <TextBlock Text="Klausur wirklich löschen?" FontSize="18" FontWeight="SemiBold"/>
+      <TextBlock Text="{Binding}" FontSize="15" FontWeight="SemiBold" TextWrapping="Wrap"/>
+      <TextBlock Text="Dabei werden auch alle erfassten Ergebnisse dieser Klausur dauerhaft gelöscht."
+                 TextWrapping="Wrap" Opacity="0.7"/>
+    </StackPanel>
+    <Grid Grid.Row="1" ColumnDefinitions="*,8,*" Margin="0,20,0,0">
+      <Button Grid.Column="0" Content="Abbrechen" HorizontalAlignment="Stretch" Click="OnCancel"/>
+      <Button Grid.Column="2" Content="Endgültig löschen" HorizontalAlignment="Stretch" Click="OnDelete"/>
+    </Grid>
+  </Grid>
+</Window>

LehrerApp.Desktop/Views/Groups/DeleteExamDialog.axaml.cs

@@ -0,0 +1,12 @@
+using Avalonia.Controls;
+using Avalonia.Interactivity;
+
+namespace LehrerApp.Desktop.Views.Groups;
+
+public partial class DeleteExamDialog : Window
+{
+    public DeleteExamDialog() => InitializeComponent();
+
+    private void OnDelete(object? sender, RoutedEventArgs e) => Close(true);
+    private void OnCancel(object? sender, RoutedEventArgs e) => Close(false);
+}

LehrerApp.Desktop/Views/Groups/ExamDialog.axaml

@@ -0,0 +1,124 @@
+<Window 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.ExamDialog"
+        x:DataType="vm:ExamDialogViewModel"
+        Title="{Binding DialogTitle}"
+        Width="640" Height="680" MinWidth="560" MinHeight="420"
+        CanResize="True" WindowStartupLocation="CenterOwner">
+
+  <Grid RowDefinitions="*,Auto" Margin="24">
+    <ScrollViewer Grid.Row="0">
+      <StackPanel Spacing="14" Margin="0,0,12,0">
+        <StackPanel Spacing="2">
+          <TextBlock Text="{Binding DialogTitle}" FontSize="18" FontWeight="SemiBold"/>
+          <TextBlock Text="{Binding SubjectDisplay}" FontSize="12" Opacity="0.6"/>
+        </StackPanel>
+
+        <StackPanel Spacing="4">
+          <TextBlock Text="Titel *" FontSize="12" Opacity="0.7"/>
+          <TextBox Text="{Binding Title}" PlaceholderText="z.B. 1. Klausur Kinetik"/>
+        </StackPanel>
+
+        <Grid ColumnDefinitions="*,12,*,12,*">
+          <StackPanel Grid.Column="0" Spacing="4">
+            <TextBlock Text="Datum *" FontSize="12" Opacity="0.7"/>
+            <TextBox Text="{Binding DateText}" PlaceholderText="TT.MM.JJJJ"/>
+          </StackPanel>
+          <StackPanel Grid.Column="2" Spacing="4">
+            <TextBlock Text="Klausurnummer" FontSize="12" Opacity="0.7"/>
+            <NumericUpDown Value="{Binding ExamNumber}" Minimum="1" Maximum="20" FormatString="0"
+                           ShowButtonSpinner="False"/>
+          </StackPanel>
+          <StackPanel Grid.Column="4" Spacing="4">
+            <TextBlock Text="Rückgabedatum" FontSize="12" Opacity="0.7"/>
+            <TextBox Text="{Binding ReturnedAtText}" PlaceholderText="TT.MM.JJJJ"/>
+          </StackPanel>
+        </Grid>
+
+        <StackPanel Spacing="4">
+          <TextBlock Text="Notizen" FontSize="12" Opacity="0.7"/>
+          <TextBox Text="{Binding Notes}" AcceptsReturn="True" Height="56" TextWrapping="Wrap"/>
+        </StackPanel>
+
+        <Separator Margin="0,4"/>
+
+        <Grid ColumnDefinitions="*,Auto">
+          <TextBlock Grid.Column="0" Text="Aufgaben" FontSize="14" FontWeight="SemiBold" VerticalAlignment="Center"/>
+          <Button Grid.Column="1" Content="＋ Aufgabe" Command="{Binding AddTaskCommand}"/>
+        </Grid>
+
+        <CheckBox Content="Gewichtung verwenden" IsChecked="{Binding UseWeighting}"/>
+
+        <Grid ColumnDefinitions="*,Auto">
+          <TextBlock Grid.Column="0" Text="{Binding TotalPointsDisplay}" FontSize="12" Opacity="0.7"
+                     VerticalAlignment="Center"/>
+          <TextBlock Grid.Column="1" Text="Achtung: noch keine Punkte vergeben" Foreground="Red" FontSize="12"
+                     IsVisible="{Binding TotalPointsWarning}" VerticalAlignment="Center"/>
+        </Grid>
+
+        <ItemsControl ItemsSource="{Binding Tasks}">
+          <ItemsControl.ItemTemplate>
+            <DataTemplate x:DataType="vm:ExamTaskEditItem">
+              <Border BorderBrush="{DynamicResource SystemControlForegroundBaseLowBrush}"
+                      BorderThickness="1" CornerRadius="4" Padding="8" Margin="0,0,0,6">
+                <StackPanel Spacing="6">
+                  <Grid ColumnDefinitions="26,*,Auto,Auto,Auto,Auto,Auto">
+                    <TextBlock Grid.Column="0" Text="{Binding Nr}" VerticalAlignment="Center" Opacity="0.6"/>
+                    <TextBox Grid.Column="1" Text="{Binding Title}" PlaceholderText="Titel der Aufgabe" Margin="0,0,6,0"/>
+                    <NumericUpDown Grid.Column="2" Value="{Binding MaxPoints}" Minimum="0" FormatString="0.##"
+                                   Width="72" ShowButtonSpinner="False" Margin="0,0,6,0" ToolTip.Tip="Maximalpunkte"/>
+                    <NumericUpDown Grid.Column="3" Value="{Binding Weight}" Minimum="0" FormatString="0.##"
+                                   Width="72" ShowButtonSpinner="False" Margin="0,0,6,0" ToolTip.Tip="Gewichtung"
+                                   IsVisible="{Binding ShowWeight}"/>
+                    <Button Grid.Column="4" Content="↑" Command="{Binding MoveUpCommand}" Padding="6,2"
+                            ToolTip.Tip="Nach oben"/>
+                    <Button Grid.Column="5" Content="↓" Command="{Binding MoveDownCommand}" Padding="6,2"
+                            ToolTip.Tip="Nach unten" Margin="4,0,0,0"/>
+                    <Button Grid.Column="6" Content="✕" Command="{Binding RemoveCommand}" Padding="6,2"
+                            ToolTip.Tip="Entfernen" Margin="4,0,0,0"/>
+                  </Grid>
+
+                  <Button Content="{Binding CompetencySummary}" Command="{Binding ToggleCompetencyPanelCommand}"
+                          HorizontalAlignment="Left" FontSize="11" Padding="6,2"/>
+
+                  <ItemsControl ItemsSource="{Binding CompetencyTagGroups}" IsVisible="{Binding IsCompetencyPanelOpen}">
+                    <ItemsControl.ItemTemplate>
+                      <DataTemplate x:DataType="vm:CompetencyTagGroup">
+                        <StackPanel Margin="12,2">
+                          <TextBlock Text="{Binding DisplayName}" FontSize="11" Opacity="0.6"/>
+                          <ItemsControl ItemsSource="{Binding Items}">
+                            <ItemsControl.ItemsPanel>
+                              <ItemsPanelTemplate>
+                                <WrapPanel/>
+                              </ItemsPanelTemplate>
+                            </ItemsControl.ItemsPanel>
+                            <ItemsControl.ItemTemplate>
+                              <DataTemplate x:DataType="vm:CompetencyTag">
+                                <ToggleButton Content="{Binding Display}" IsChecked="{Binding IsSelected}"
+                                              Margin="0,2,6,2" FontSize="11" Padding="6,2"/>
+                              </DataTemplate>
+                            </ItemsControl.ItemTemplate>
+                          </ItemsControl>
+                        </StackPanel>
+                      </DataTemplate>
+                    </ItemsControl.ItemTemplate>
+                  </ItemsControl>
+                </StackPanel>
+              </Border>
+            </DataTemplate>
+          </ItemsControl.ItemTemplate>
+        </ItemsControl>
+
+        <TextBlock Text="{Binding ValidationMessage}" Foreground="Red" FontSize="12"
+                   IsVisible="{Binding ValidationMessage, Converter={x:Static StringConverters.IsNotNullOrEmpty}}"/>
+      </StackPanel>
+    </ScrollViewer>
+
+    <Grid Grid.Row="1" ColumnDefinitions="*,8,*" Margin="0,20,0,0">
+      <Button Grid.Column="0" Content="Abbrechen" HorizontalAlignment="Stretch" Click="OnCancel"/>
+      <Button Grid.Column="2" Content="{Binding SaveButtonText}"
+              HorizontalAlignment="Stretch" Click="OnSave"/>
+    </Grid>
+  </Grid>
+</Window>

LehrerApp.Desktop/Views/Groups/ExamDialog.axaml.cs

@@ -0,0 +1,21 @@
+using Avalonia.Controls;
+using Avalonia.Interactivity;
+using LehrerApp.Desktop.ViewModels.Groups;
+
+namespace LehrerApp.Desktop.Views.Groups;
+
+public partial class ExamDialog : Window
+{
+    public ExamDialog() => InitializeComponent();
+
+    private void OnSave(object? s, RoutedEventArgs e)
+    {
+        if (DataContext is ExamDialogViewModel vm && vm.SaveCommand.CanExecute(null))
+        {
+            vm.SaveCommand.Execute(null);
+            if (vm.Result is not null) Close(true);
+        }
+    }
+
+    private void OnCancel(object? s, RoutedEventArgs e) => Close(false);
+}

LehrerApp.Desktop/Views/Groups/GroupDetailView.axaml

@@ -2,6 +2,7 @@
              xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
              xmlns:vm="clr-namespace:LehrerApp.Desktop.ViewModels.Groups"
              xmlns:views="clr-namespace:LehrerApp.Desktop.Views.Groups"
+             xmlns:models="clr-namespace:LehrerApp.Core.Models;assembly=LehrerApp.Core"
              x:Class="LehrerApp.Desktop.Views.Groups.GroupDetailView"
              x:DataType="vm:GroupDetailViewModel">
 
@@ -66,17 +67,70 @@
 
       <!-- Tab: Klausuren -->
       <ContentPage Header="Klausuren">
-        <DataGrid ItemsSource="{Binding Exams}"
-                  AutoGenerateColumns="False"
-                  IsReadOnly="True"
-                  GridLinesVisibility="Horizontal"
-                  CanUserReorderColumns="False">
-          <DataGrid.Columns>
-            <DataGridTextColumn Header="Datum"  Binding="{Binding Date}"        Width="110"/>
-            <DataGridTextColumn Header="Titel"  Binding="{Binding Title}"       Width="*"/>
-            <DataGridTextColumn Header="Status" Binding="{Binding StatusLabel}" Width="130"/>
-          </DataGrid.Columns>
-        </DataGrid>
+        <Grid RowDefinitions="Auto,*">
+          <StackPanel Grid.Row="0" Orientation="Horizontal" Spacing="8" Margin="0,0,0,8"
+                      IsVisible="{Binding SelectedExam, Converter={x:Static ObjectConverters.IsNotNull}}">
+            <Button Content="Bearbeiten"    Command="{Binding EditExamCommand}"/>
+            <Button Content="Duplizieren"   Command="{Binding DuplicateExamCommand}"/>
+            <SplitButton Content="Status ▸" Command="{Binding AdvanceExamStatusCommand}">
+              <SplitButton.Flyout>
+                <MenuFlyout Placement="BottomEdgeAlignedLeft">
+                  <MenuItem Header="Geplant"       Command="{Binding SetExamStatusCommand}"
+                            CommandParameter="{x:Static models:ExamStatus.Planned}"/>
+                  <MenuItem Header="Durchgeführt"  Command="{Binding SetExamStatusCommand}"
+                            CommandParameter="{x:Static models:ExamStatus.Conducted}"/>
+                  <MenuItem Header="Korrigiert"    Command="{Binding SetExamStatusCommand}"
+                            CommandParameter="{x:Static models:ExamStatus.Graded}"/>
+                  <MenuItem Header="Zurückgegeben" Command="{Binding SetExamStatusCommand}"
+                            CommandParameter="{x:Static models:ExamStatus.Returned}"/>
+                </MenuFlyout>
+              </SplitButton.Flyout>
+            </SplitButton>
+            <Button Content="Löschen"       Command="{Binding DeleteExamCommand}"/>
+          </StackPanel>
+          <DataGrid Grid.Row="1" ItemsSource="{Binding Exams}"
+                    SelectedItem="{Binding SelectedExam}"
+                    AutoGenerateColumns="False"
+                    IsReadOnly="True"
+                    GridLinesVisibility="Horizontal"
+                    CanUserReorderColumns="False">
+            <DataGrid.Columns>
+              <DataGridTextColumn Header="Datum"  Binding="{Binding Date}"  Width="110"/>
+              <DataGridTextColumn Header="Titel"  Binding="{Binding Title}" Width="*"/>
+              <DataGridTemplateColumn Header="Status" Width="150">
+                <DataGridTemplateColumn.CellTemplate>
+                  <DataTemplate x:DataType="vm:ExamSummary">
+                    <Border Background="{Binding StatusColorHex}" CornerRadius="4"
+                            Padding="8,2" HorizontalAlignment="Left">
+                      <TextBlock Text="{Binding StatusLabel}" FontSize="12" Foreground="White"/>
+                    </Border>
+                  </DataTemplate>
+                </DataGridTemplateColumn.CellTemplate>
+              </DataGridTemplateColumn>
+              <DataGridTextColumn Header="Rückgabe" Binding="{Binding ReturnedAtDisplay}" Width="100"/>
+            </DataGrid.Columns>
+            <DataGrid.ContextMenu>
+              <ContextMenu>
+                <MenuItem Header="Bearbeiten"    Command="{Binding EditExamCommand}"/>
+                <MenuItem Header="Duplizieren"   Command="{Binding DuplicateExamCommand}"/>
+                <MenuItem Header="Status">
+                  <MenuItem Header="Weiter" Command="{Binding AdvanceExamStatusCommand}"/>
+                  <Separator/>
+                  <MenuItem Header="Geplant"       Command="{Binding SetExamStatusCommand}"
+                            CommandParameter="{x:Static models:ExamStatus.Planned}"/>
+                  <MenuItem Header="Durchgeführt"  Command="{Binding SetExamStatusCommand}"
+                            CommandParameter="{x:Static models:ExamStatus.Conducted}"/>
+                  <MenuItem Header="Korrigiert"    Command="{Binding SetExamStatusCommand}"
+                            CommandParameter="{x:Static models:ExamStatus.Graded}"/>
+                  <MenuItem Header="Zurückgegeben" Command="{Binding SetExamStatusCommand}"
+                            CommandParameter="{x:Static models:ExamStatus.Returned}"/>
+                </MenuItem>
+                <Separator/>
+                <MenuItem Header="Löschen"       Command="{Binding DeleteExamCommand}"/>
+              </ContextMenu>
+            </DataGrid.ContextMenu>
+          </DataGrid>
+        </Grid>
       </ContentPage>
 
       <!-- Tab: Noten -->

LehrerApp.Desktop/Views/Groups/GroupDetailView.axaml.cs

@@ -1,5 +1,6 @@
 using Avalonia.Controls;
 using LehrerApp.Core.Interfaces;
+using LehrerApp.Core.Models;
 using LehrerApp.Desktop.ViewModels.Groups;
 using Microsoft.Extensions.DependencyInjection;
 
@@ -13,7 +14,13 @@ public partial class GroupDetailView : UserControl
     {
         base.OnDataContextChanged(e);
         if (DataContext is GroupDetailViewModel vm)
-            vm.OnAddStudent = ShowAddStudentDialog;
+        {
+            vm.OnAddStudent      = ShowAddStudentDialog;
+            vm.OnAddExam         = ShowAddExamDialog;
+            vm.OnEditExam        = ShowEditExamDialog;
+            vm.OnDuplicateExam   = ShowDuplicateExamDialog;
+            vm.OnConfirmDeleteExam = ShowDeleteExamDialog;
+        }
     }
 
     private async Task<bool> ShowAddStudentDialog()
@@ -32,4 +39,37 @@ public partial class GroupDetailView : UserControl
 
         return await dialog.ShowDialog<bool>(owner);
     }
+
+    private Task<bool> ShowAddExamDialog(Guid groupId) =>
+        ShowExamDialog(groupId, editingExam: null, duplicateSource: null);
+
+    private Task<bool> ShowEditExamDialog(Exam exam) =>
+        ShowExamDialog(exam.GroupId, editingExam: exam, duplicateSource: null);
+
+    private Task<bool> ShowDuplicateExamDialog(Exam exam) =>
+        ShowExamDialog(exam.GroupId, editingExam: null, duplicateSource: exam);
+
+    private async Task<bool> ShowExamDialog(Guid groupId, Exam? editingExam, Exam? duplicateSource)
+    {
+        if (DataContext is not GroupDetailViewModel vm || vm.Group is null) return false;
+
+        var dialogVm = new ExamDialogViewModel(
+            App.Services.GetRequiredService<IExamRepository>(),
+            App.Services.GetRequiredService<ICompetencyDomainRepository>(),
+            groupId, vm.Group.SubjectId, vm.Group.GradeLevel, vm.Group.GradingSystem,
+            vm.Group.Subject ?? "", editingExam, duplicateSource);
+
+        var dialog = new ExamDialog { DataContext = dialogVm };
+        var owner = TopLevel.GetTopLevel(this) as Window;
+        if (owner is null) return false;
+
+        return await dialog.ShowDialog<bool>(owner);
+    }
+
+    private async Task<bool> ShowDeleteExamDialog(ExamSummary exam)
+    {
+        var dialog = new DeleteExamDialog { DataContext = exam.Title };
+        var owner = TopLevel.GetTopLevel(this) as Window;
+        return owner is not null && await dialog.ShowDialog<bool>(owner);
+    }
 }

TODO.md

@@ -32,20 +32,21 @@ Modelle `Exam`, `ExamTask`, `GradingKeyEntry`, `ExamResult` existieren bereits i
 [Exam.cs](LehrerApp.Core/Models/Exam.cs), Repositories ebenfalls. Die komplette UI fehlt.
 
 ### 1.1 Klausur anlegen und verwalten
-- [ ] **1.1.1** Dialog `AddExamDialog` — Titel, Datum, Fach, Klausurnummer, Notizen.
-      Ersetzt den TODO-Stub `AddExam()` in [GroupViewModels.cs:189](LehrerApp.Desktop/ViewModels/Groups/GroupViewModels.cs#L189).
-- [ ] **1.1.2** Klausur bearbeiten/löschen (Kontextmenü im Klausuren-Tab, Löschen mit Rückfrage).
-- [ ] **1.1.3** Statuswechsel `Planned → Conducted → Graded → Returned` per Button,
+- [x] **1.1.1** Dialog `AddExamDialog` — Titel, Datum, Fach, Klausurnummer, Notizen.
+      Ersetzt den TODO-Stub `AddExam()` in [GroupViewModels.cs](LehrerApp.Desktop/ViewModels/Groups/GroupViewModels.cs).
+      Umgesetzt als `ExamDialog`/`ExamDialogViewModel`.
+- [x] **1.1.2** Klausur bearbeiten/löschen (Kontextmenü im Klausuren-Tab, Löschen mit Rückfrage).
+- [x] **1.1.3** Statuswechsel `Planned → Conducted → Graded → Returned` per Button,
       inkl. Farbcodierung des Status im DataGrid.
-- [ ] **1.1.4** Klausur aus bestehender Klausur duplizieren (Aufgaben + Notenschlüssel übernehmen,
+- [x] **1.1.4** Klausur aus bestehender Klausur duplizieren (Aufgaben + Notenschlüssel übernehmen,
       neues Datum) — für Parallelkurse.
 
 ### 1.2 Aufgabenstruktur (`ExamTask`)
-- [ ] **1.2.1** Editor für die Aufgabenliste: Nr., Titel, Maximalpunkte, Gewichtung.
-      Zeilen hinzufügen/entfernen/umsortieren.
-- [ ] **1.2.2** Automatische Anzeige der Gesamtpunktzahl, Warnung bei 0 Punkten.
+- [x] **1.2.1** Editor für die Aufgabenliste: Nr., Titel, Maximalpunkte, Gewichtung.
+      Zeilen hinzufügen/entfernen/umsortieren. Umgesetzt im `ExamDialog` (Teil von 1.1.1).
+- [x] **1.2.2** Automatische Anzeige der Gesamtpunktzahl, Warnung bei 0 Punkten.
 - [ ] **1.2.3** Optional: Teilaufgaben (a/b/c) — erfordert Modellerweiterung, vorher entscheiden.
-- [ ] **1.2.4** Zuordnung von Kompetenzen (`CompetencyItem`) zu einzelnen Aufgaben —
+- [x] **1.2.4** Zuordnung von Kompetenzen (`CompetencyItem`) zu einzelnen Aufgaben —
       Voraussetzung für die Kompetenzauswertung in 8.3.
 
 ### 1.3 Notenschlüssel