private void btnAddStudent_Click(object sender, RoutedEventArgs e)
        {
            try
            {
                AddStudentWindow addStudentWindow = new AddStudentWindow();
                if (addStudentWindow.ShowDialog() == true)
                {
                    Student student = new Student()
                    {
                        Username   = addStudentWindow.Username,
                        FirstName  = addStudentWindow.FirstName,
                        MiddleName = addStudentWindow.MiddleName,
                        LastName   = addStudentWindow.LastName,
                        EGN        = addStudentWindow.EGN,
                        ClassId    = addStudentWindow.ClassId
                    };

                    string secret = Crypto.GenerateRandomSecret();
                    student.Username = Crypto.EncryptStringAES(student.Username, secret);
                    string password = Crypto.EncryptStringAES(addStudentWindow.Password, secret);

                    if (client.RegisterStudent(student, password, secret))
                    {
                        UpdateStudentViews();
                        MessageBox.Show("Ученикът беше добавен успешно");
                    }
                    else
                    {
                        MessageBox.Show("Ученикът не е валиден или вече съществува");
                    }
                }
            }
            catch (Exception ex)
            {
                MessageBox.Show(Application.Current.Resources["defaultErrorMessage"].ToString(),
                                "Грешка", MessageBoxButton.OK, MessageBoxImage.Error);
            }
        }
        private void btnAddStudent_Click(object sender, RoutedEventArgs e)
        {
            try
            {
                AddStudentWindow addStudentWindow = new AddStudentWindow();
                if (addStudentWindow.ShowDialog() == true)
                {
                    Student student = new Student()
                    {
                        Username = addStudentWindow.Username,
                        FirstName = addStudentWindow.FirstName,
                        MiddleName = addStudentWindow.MiddleName,
                        LastName = addStudentWindow.LastName,
                        EGN = addStudentWindow.EGN,
                        ClassId = addStudentWindow.ClassId
                    };

                    string secret = Crypto.GenerateRandomSecret();
                    student.Username = Crypto.EncryptStringAES(student.Username, secret);
                    string password = Crypto.EncryptStringAES(addStudentWindow.Password, secret);

                    if(client.RegisterStudent(student, password, secret))
                    {
                        UpdateStudentViews();
                        MessageBox.Show("Ученикът беше добавен успешно");   
                    }
                    else
                    {
                        MessageBox.Show("Ученикът не е валиден или вече съществува");
                    }
                }
            }
            catch (Exception ex)
            {
                MessageBox.Show(Application.Current.Resources["defaultErrorMessage"].ToString(), 
                    "Грешка", MessageBoxButton.OK, MessageBoxImage.Error);
            }
        }