private async Task Save() { this.Lesson.Date = this.LessonDate; this.Lesson.Description = this.Description; this.Lesson.Group = this.IsGroupsAvailable ? this.SelectedGroup : null; this.Lesson.Stream = this.SelectedStream; this.Lesson.LessonType = this.SelectedLessonType.Type; this.Lesson.Schedule = this.SelectedSchedule; if (!this.IsGroupsAvailable) { this.Lesson.Group = null; } _originalEntity.Apply(this.Lesson); _db.SetLessonOrder(_originalEntity); if (this.Lesson.Id == default) { _originalEntity.CreationDate = DateTime.Now; _db.Lessons.Add(_originalEntity); } await _db.SaveChangesAsync(); if (!this.SetAllPresent) { return; } await RegisterAllStudents(_originalEntity); }