How to pass a "path" to an object member in C#?

Question

Say I have

public class family
{
   public person father;
   public person mother;
   public person[] child;
}

public class person
{
   public string name;
   public int age;
}

What I want to do is add a function to family that will allow me to specify the location I want a new person saved to.

If there were C I would pass in a pointer to person so I could point it at a new person but I am somewhat new to C# and don't know what to do here. So I want it to look something like this:

public void SavePerson(int newAge, string newName, ??? location)
{
   person addMe = new person();
   addMe.age = newAge;
   addMe.name = newName;
   location = addMe;
}

I don't want to change the previous content of location. If it used to point at Frank, I want to keep Frank just the way he was, I just want it to now point at John (because other things may still be pointing at Frank)

The reason I need this is because I have an interface and classes much more complicated than this. But there is one class I need to create and save a lot (and it appears all over in a large NHibernate created object) and I would like to roll that into one function for simplicity's sake.

Answer 1

The idiomatic C# way of doing things would be to simply return the new object:

public Person CreatePerson(int age, string name)
{
    Person person = new Person();
    person.Age = age;
    person.Name = name;
    return person;
}

Usage:

family.Children[0] = CreatePerson(11, "Frank");
family.Children[1] = CreatePerson(15, "John");

---

Alternatively, you can pass the Person[] and an index to the method:

public void SavePerson(int age, string name, Person[] persons, int index)
{
    persons[index] = new Person();
    persons[index].Age = age;
    persons[index].Name = name;
}

Usage:

SavePerson(11, "Frank", family.Children, 0);
SavePerson(15, "John",  family.Children, 1);

But I'm not sure why you'd want to delegate this responsibility to your factory method.

---

If you really want to manipulate variable contents by reference, you can do that using the ref or out keyword:

public void SavePerson(int age, string name, out Person person)
{
    person = new Person();
    person.Age = age;
    person.Name = name;
}

Usage:

SavePerson(11, "Frank", out family.Children[0]);
SavePerson(15, "John",  out family.Children[1]);

See: Parameter passing in C#

See: When is using the C# ref keyword ever a good idea?

---

But why not simply use object and collection initializers?

Person mom = new Person { Age = 41, Name = "Martha" };
Person dad = new Person { Age = 43, Name = "Dan"    };

Family family = new Family(mom, dad)
{
    new Person { Age = 11, Name = "Frank" },
    new Person { Age = 15, Name = "John"  },
};

See: Object and Collection Initializers