public void DeleteStudent(int userId)
{
var deleteStudent = "DELETE FROM students WHERE userId = @userId";
SqlCommand commandDeleteStudent = new SqlCommand(deleteStudent, connection);
commandDeleteStudent.Parameters.AddWithValue("@userId", userId);
connection.Open();
commandDeleteStudent.ExecuteNonQuery();
connection.Close();
var grades = repository.GetStudentGrades(userId);
foreach (Grade grade in grades)
{
repository.DeleteGrade(grade.ID);
}
DeleteUser(userId);
}