public ProfessorWindow() { InitializeComponent(); userLabel.Text += professor.degree + " " + professor.Name + " " + professor.Surname; List <Subject> subjectsList = otherData.GetAllAssignedSubjects(); foreach (Subject subject in subjectsList) { if (professor.Id == otherData.FindSubjectProfessorId(subject.Title)) { subjectsBox.Items.Add(subject.Title); currentSubjectsList.Add(subject); } } if (subjectsBox.Items.Count == 0) { groupsBox.Visible = false; GradeStudentLabelsAndButtonFalse(); } }