Question

I find it difficult to determine the responsiblity of classes: do i have to put this method in this class or should I put this method in another class? For example, imagine a simple User class with an id, forname, lastname and password. Now you have an userId and you want the forname and lastname, so you create a method like: public User GetUserById(int id){}. Next you want to show list of all the users, so you create another method: public List GetAllUsers(){}. And offcourse you want to update, delete and save a user. This gives us 5 methods:

public bool SaveUser(User user);
public bool UpdateUser(User user);
public bool DeleteUser(User user);
public User GetUserById(int id);
public List<User> GetAllUsers();

So my question is: do you put all these methods in the User class? Or do you create another data class (UserData class) which may connect to the database and contain all these methods?

Answer 1

What you are describing here is basically a choice between the Active Record Pattern or the Repository Pattern. I’d advise you to read up on those patterns and choose whichever one fits your application / experience / toolset.