Nested class: Cannot access non-static field in static context

Question

I have a class C with some internal variables. It has a nested class N that wants to access the variables in C. Neither C nor N are static, although C has some static methods and variables. When I try to access a non-static variable in C from N I get the squiggly underline and the message "Cannot access non-static field [fieldname] in static context".

This seems to have something to do with the nested class, since I can access the variable fine from the enclosing class itself.

ReSharper suggests I make _t static but that isn't an option. How do I deal with this?

public sealed partial class C
{
    string _t;

    class N
    {
        void m()
        {
            _t = "fie"; // Error occurs here
        }
    }
}

possible duplicate of Inner class and Outer class in c# and stackoverflow.com/questions/2367015/… — Ben Voigt
– Ben Voigt, Commented Jun 11, 2012 at 23:51

Ben Voigt · Accepted Answer · 2012-06-11 23:48:22Z

16

This isn't Java, and you don't have inner classes.

An instance of a nested class is not associated with any instance of the outer class, unless you make an association by storing a reference (aka handle/pointer) inside the constructor.

public sealed partial class C
{
    string _t;

    class N
    {
        readonly C outer;

        public N(C parent) { outer = parent; }

        void m()
        {
            outer._t = "fie"; // Error is gone
        }
    }
}

answered Jun 11, 2012 at 23:48

Ben Voigt

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2 Comments

Sisiutl Over a year ago

The O'Reilly "Nutshell" book (Albahari & Albahari) says "A nested type ... can access the enclosing type's private members and everything else the enclosing type can access."

Ben Voigt Over a year ago

@Sisiutl: This has nothing to do with accessibility. Because of the rule "Nutshell" mentions, my code works even with private string _t;. Without that rule, you would need either internal or public. A static method also has access to private members, but needs to supply an instance reference before using non-static members.

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