/// <summary>
/// This method requires a user id and gets all courses that the user is not subscribed to.
/// </summary>
/// <param name="id">The id</param>
/// <returns>Returns a list of the courses that the user is not subscribed to.</returns>
public List <Course> getNonSubscribedCourses(int id)
{
QueryStrings queryStrings = new QueryStrings();
List <Course> allCourses = queryStrings.getNonSubscribedCourses(id);
return(allCourses);
}