егор хранилище закончил свою часть

University/UniversityContracts/BindingModels/DisciplineBindingModel.cs

@@ -14,5 +14,6 @@ namespace UniversityContracts.BindingModels
         public int TeacherId { get; set; }
         public string Name { get; set; } = string.Empty;
         public string Description { get; set; } = string.Empty;
+        public Dictionary<int, (IStudentModel, int)> StudentDisciplines { get; set; } = new();
     }
 }

University/UniversityContracts/ViewModels/DisciplineViewModel.cs

@@ -16,5 +16,10 @@ namespace UniversityContracts.ViewModels
         public string Name { get; set; } = string.Empty;
         [DisplayName("Описание дисциплины")]
         public string Description { get; set; } = string.Empty;
+        public Dictionary<int, IStudentModel> StudentDisciplines
+        {
+            get;
+            set;
+        } = new();
     }
 }

University/UniversityDatabaseImplement/Implements/DisciplineStorage.cs

@@ -18,7 +18,7 @@ namespace UniversityDatabaseImplement.Implements
         public DisciplineViewModel? Delete(DisciplineBindingModel model)
         {
             using var context = new UniversityDatabase();
-            var element = context.Disciplines.FirstOrDefault(rec => rec.Id == model.Id);
+            var element = context.Disciplines.Include(x => x.Students).FirstOrDefault(rec => rec.Id == model.Id);
             if (element != null)
             {
                 context.Disciplines.Remove(element);
@@ -35,7 +35,7 @@ namespace UniversityDatabaseImplement.Implements
                 return null;
             }
             using var context = new UniversityDatabase();
-            return context.Disciplines
+            return context.Disciplines.Include(x => x.Students).ThenInclude(x => x.Student)
             .Include(x => x.Teacher)
             .FirstOrDefault(x =>
            (!string.IsNullOrEmpty(model.Name) && x.Name == model.Name) || (model.Id.HasValue && x.Id == model.Id)) ?.GetViewModel;
@@ -50,6 +50,8 @@ namespace UniversityDatabaseImplement.Implements
             }
             using var context = new UniversityDatabase();
             return context.Disciplines
+            .Include(x => x.Students)
+            .ThenInclude(x => x.Student)
             .Where(x => x.Name.Contains(model.Name) || x.Description.Contains(model.Description)  || x.Id == model.Id || x.TeacherId == model.TeacherId)
             .Include(x => x.Teacher)
            .Select(x => x.GetViewModel)
@@ -60,6 +62,9 @@ namespace UniversityDatabaseImplement.Implements
         {
             using var context = new UniversityDatabase();
             return context.Disciplines
+            .Include(x => x.Students)
+            .ThenInclude(x => x.Student)
+            .ToList()
             .Select(x => x.GetViewModel)
            .ToList();
         }
@@ -67,7 +72,7 @@ namespace UniversityDatabaseImplement.Implements
         public DisciplineViewModel? Insert(DisciplineBindingModel model)
         {
             using var context = new UniversityDatabase();
-            var newDiscipline = Discipline.Create(model);
+            var newDiscipline = Discipline.Create(context, model);
             if (newDiscipline == null)
             {
                 return null;
@@ -80,14 +85,25 @@ namespace UniversityDatabaseImplement.Implements
         public DisciplineViewModel? Update(DisciplineBindingModel model)
         {
             using var context = new UniversityDatabase();
-            var discipline = context.Disciplines.FirstOrDefault(x => x.Id == model.Id);
-            if (discipline == null)
+            using var transaction = context.Database.BeginTransaction();
+            try
             {
-                return null;
+                    var discipline = context.Disciplines.FirstOrDefault(x => x.Id == model.Id);
+                if (discipline == null)
+                {
+                    return null;
+                }
+                discipline.Update(model);
+                context.SaveChanges();
+                discipline.UpdateStudents(context, model);
+                transaction.Commit();
+                return discipline.GetViewModel;
+            }
+            catch
+            {
+                transaction.Rollback();
+                throw;
             }
-            discipline.Update(model);
-            context.SaveChanges();
-            return discipline.GetViewModel;
         }
     }
 }

University/UniversityDatabaseImplement/Models/Discipline.cs

@@ -21,23 +21,23 @@ namespace UniversityDatabaseImplement.Models
         [Required]
         public string Description { get; private set; } = string.Empty;
         public virtual Teacher Teacher { get; set; } = new();
-        [ForeignKey("DisciplineId")]
-        public virtual List<StudentDiscipline> StudentDisciplines { get; set; } = new();
-        public static Discipline? Create(DisciplineBindingModel model)
+        private Dictionary<int, IStudentModel>? _studentDisciplines = null;
+        [NotMapped]
+        public Dictionary<int, IStudentModel> StudentDisciplines
         {
-            if (model == null)
+            get
             {
-                return null;
+                if (_studentDisciplines == null)
+                {
+                    _studentDisciplines = Students
+                    .ToDictionary(recPC => recPC.StudentId, recPC => recPC.Student as IStudentModel);
+                }
+                return _studentDisciplines;
             }
-            return new Discipline()
-            {
-                Id = model.Id,
-                TeacherId = model.TeacherId,
-                Name = model.Name,
-                Description = model.Description,
-            };
         }
-        public static Discipline Create(DisciplineViewModel model)
+        [ForeignKey("DisciplineId")]
+        public virtual List<StudentDiscipline> Students { get; set; } = new();
+        public static Discipline Create(UniversityDatabase context, DisciplineBindingModel model)
         {
             return new Discipline()
             {
@@ -45,6 +45,11 @@ namespace UniversityDatabaseImplement.Models
                 TeacherId = model.TeacherId,
                 Name = model.Name,
                 Description = model.Description,
+                Students = model.StudentDisciplines.Select(x => new
+               StudentDiscipline
+                {
+                    Student = context.Students.First(y => y.Id == x.Key)
+                }).ToList()
             };
         }
         public void Update(DisciplineBindingModel model)
@@ -58,12 +63,41 @@ namespace UniversityDatabaseImplement.Models
             Name = model.Name;
             Description = model.Description;
         }
+        public void UpdateStudents(UniversityDatabase context,
+      DisciplineBindingModel model)
+        {
+            var studentDisciplines = context.StudentDisciplines.Where(rec => rec.DisciplineId == model.Id).ToList();
+            if (studentDisciplines != null && studentDisciplines.Count > 0)
+            { // удалили те, которых нет в модели
+                context.StudentDisciplines.RemoveRange(studentDisciplines.Where(rec
+               => !model.StudentDisciplines.ContainsKey(rec.StudentId)));
+                context.SaveChanges();
+                // обновили количество у существующих записей
+                foreach (var updateStudent in studentDisciplines)
+                {
+                    model.StudentDisciplines.Remove(updateStudent.StudentId);
+                }
+                context.SaveChanges();
+            }
+            var discipline = context.Disciplines.First(x => x.Id == Id);
+            foreach (var pc in model.StudentDisciplines)
+            {
+                context.StudentDisciplines.Add(new StudentDiscipline
+                {
+                    Discipline = discipline,
+                    Student = context.Students.First(x => x.Id == pc.Key)
+                });
+                context.SaveChanges();
+            }
+            _studentDisciplines = null;
+        }
         public DisciplineViewModel GetViewModel => new()
         {
             Id = Id,
             TeacherId = TeacherId,
             Name = Name,
             Description = Description,
+            StudentDisciplines = StudentDisciplines,
         };
     }
 }

University/UniversityDatabaseImplement/UniversityDatabase.cs

@@ -24,5 +24,6 @@ namespace UniversityDatabaseImplement
         public virtual DbSet<Teacher> Teachers { set; get; }
         public virtual DbSet<Discipline> Disciplines { set; get; }
         public virtual DbSet<Statement> Statements { set; get; }
+        public virtual DbSet<StudentDiscipline> StudentDisciplines { set; get; }
     }
 }