Duplicated Memory on .NET using two lists

Question

I'm working on a small app on .NET, I need to point the same data with 2 diferent lists, I'm wondering if perhaps the memory is duplicated, for example

public class Person
{
    public string name;
    public int age;

    ....
    public Person(name, age)
    {
        this.name = name;
        this.age = age;
    }
}

SortedList<string> names;
SortedList<int> ages;

Person person1 = new Person("juan",23);

names.add("juan",person1);
ages.add(23,person1);

I guess that .NET as Java will not duplicate the object Person, so it will be keeped, so if I do this:

names("juan").age = 24

Will change the object in both lists.

Is it right?

Thank you.

Answer 1

Because Person is a class, you are only putting a reference into the list, so each list will have a reference to the same person. The Person object will indeed not be duplicated, and names["juan"] will de-reference the original object.

However! That doesn't make the code faultless:

• there might be more than one person aged 23; SortedList<,> won't like that
• changing the age via names["juan"] won't automatically update ages; ages[24] will fail

If Person was a struct, then the Person would be copied every time you assign it (but: this is not a good candidate for a struct; don't do that)

Answer 2

To test reference equality, you can always do:

bool equals = ReferenceEquals(obj1, obj2); 
//in your case, obj1 = names["juan"], and obj2 = ages[23]

If reference is the same that means any change on it will be reflected on variables that reference to the same object.

---

In your case, yes they are just the same reference in both lists.. So if you do anything on the reference, be it on person1, names["juan"] or ages[23] it will be reflected everywhere. That said, your collection should look like:

Person person1 = new Person();
SortedList<string, Person> names = new SortedList<string, Person>();
SortedList<int, Person> ages = new SortedList<int, Person>();

names.Add("juan", person1);
ages.Add(23, person1);

//names["juan"].age
//ages[23].age 
//etc

Answer 3

Yes, This Will change the object in both lists.

if you want to provident this i suggest to overload the "=" operator (explicit )