private void DeleteDeclaration()
        {
            if (!String.IsNullOrWhiteSpace(declarationIDTextBox.Text))
            {
                Student_Major selectedDeclaration = declarationListBox.SelectedItem as Student_Major;

                RegistrationDatabase.Student_Major.Remove(selectedDeclaration);

                try {
                    RegistrationDatabase.SaveChanges();
                }
                catch (Exception ex) {
                    MessageBox.Show(ex.Message);
                }

                BindDeclarationList();
            }
        }
        private void AddDeclaration()
        {
            if (!String.IsNullOrWhiteSpace(majorIDTextBox.Text) &&
                !String.IsNullOrWhiteSpace(studentIDTextBox.Text))
            {
                Student_Major newDeclaration = new Student_Major {
                    Major_Id   = Convert.ToInt32(majorIDTextBox.Text),
                    Student_Id = Convert.ToInt32(studentIDTextBox.Text)
                };

                RegistrationDatabase.Student_Major.Add(newDeclaration);

                try {
                    RegistrationDatabase.SaveChanges();
                }
                catch (Exception ex) {
                    MessageBox.Show(ex.Message);
                }

                BindDeclarationList();
            }
        }
        private void DeclarationListBox_SelectedIndexChanged(object sender, EventArgs e)
        {
            Student_Major selectedDeclaration = declarationListBox.SelectedItem as Student_Major;

            declarationIDTextBox.Text = selectedDeclaration.Id.ToString();
        }