how to get access to private members of nested class?

Question

Background: I have enclosed (parent) class E with nested class N with several instances of N in E. In the enclosed (parent) class I am doing some calculations and I am setting the values for each instance of nested class. Something like this:

n1.field1 = ...;
n1.field2 = ...;
n1.field3 = ...;
n2.field1 = ...;
...

It is one big eval method (in parent class). My intention is -- since all calculations are in parent class (they cannot be done per nested instance because it would make code more complicated) -- make the setters only available to parent class and getters public.

And now there is a problem:

• when I make the setters private, parent class cannot acces them
• when I make them public, everybody can change the values
• and C# does not have friend concept
• I cannot pass values in constructor because lazy evaluation mechanism is used (so the instances have to be created when referencing them -- I create all objects and the calculation is triggered on demand)

I am stuck -- how to do this (limit access up to parent class, no more, no less)?

---

I suspect I'll get answer-question first -- "but why you don't split the evaluation per each field" -- so I answer this by example: how do you calculate min and max value of a collection? In a fast way? The answer is -- in one pass. This is why I have one eval function which does calculations and sets all fields at once.

Answer 1

make the fields "protected internal"

if the nested classes are private you could use obly "internal" to those fields.

Answer 2

You could declare inside E a private interface IN, explicitly implemented by N. This interface would expose the members of N accessible only by E :

public class E
{
    public void Foo()
    {
      IN n = new N();
      n.Field1 = 42;
    }

    public class N : IN
    {
        private int _field1;

        int IN.Field1
        {
            get { return _field1; }
            set { _field1 = value; }
        }
    }

    private interface IN
    {
        int Field1 { get; set; }
    }
}