using System;

using System.Collections.Generic;

​

public class Entry {

    // concrete, final

}

​

public interface IEntryable {

    void FromEntry(Entry e);

    Entry ToEntry();

}

​

public class Character : IEntryable {

    public void FromEntry(Entry e) {

        // this should be final

        Console.WriteLine("Base import");

        ImportCustomFields(e);

    }

    public virtual void ImportCustomFields(Entry e) {

    }

    public Entry ToEntry() {

        // this should be final

        Entry e = new Entry();

        Console.WriteLine("Base export");

        ExportCustomFields(e);

        return e;

    }

    public virtual void ExportCustomFields(Entry e) {

        // or anyway you like

    }

}

​

// version 1

public class CharacterStorage<TChar> where TChar : Character, new() {

    // this version uses generics; I am wary of generics in general,

    // but this one seem to be a sensible case

    public List<TChar> myCharacters = new List<TChar>();    

    public void Import() {

        // ..

        TChar instance = new TChar();

        myCharacters.Add(instance);

        instance.FromEntry(new Entry());

    }

}

​

// version 2

public class CharacterStorage2 {

    // this version does not use generics; it even works by itself

    // but a disadvantage is that it is LESS elegant for the subclass

    public List<Character> myCharacters = new List<Character>();    

    public virtual Character GenerateCharacter() {

        return new Character();

    }

    public void Import() {

        // ..

        Character instance = GenerateCharacter();

        myCharacters.Add(instance);

        instance.FromEntry(new Entry());

    }

}

​

// THE FOLLOWING ARE OUTSIDE ENGINE

// I need to have new data for each of my Character(s), so I need to subclass both

​

public class MyCharacter : Character {

    public override void ImportCustomFields(Entry e) {

        Console.WriteLine("New import");

    }

}

public class MyCharacterStorage : CharacterStorage<MyCharacter> {

    // this extends version 1, with generics

    public void NoteworthyIssue() {

        Console.WriteLine(myCharacters.ToString());

    }

}

​

public class MyCharacterStorage2 : CharacterStorage2 {

    // this extends version 2, without generics

    public override Character GenerateCharacter() {

        return new MyCharacter();

    }

    public void NoteworthyIssue() {

        Console.WriteLine(myCharacters.ToString());

    }

}

public class Program

{

    public static void Main()

    {

        MyCharacterStorage myStorage = new MyCharacterStorage();

        myStorage.Import();

        myStorage.NoteworthyIssue();

        MyCharacterStorage2 myStorage2 = new MyCharacterStorage2();

        myStorage2.Import();

        myStorage2.NoteworthyIssue();

    }

}