NGWS SDK Documentation  

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3.3.2 Accessibility domains

The accessibility domain of a member is the (possibly disjoint) sections of program text in which access to the member is permitted. For purposes of defining the accessibility domain of a member, a member is said to be top-level if it is not declared within a type, and a member is said to be nested if it is declared within another type. Furthermore, the program text of a project is defined as all program text contained in all source files of the project, and the program text of a type is defined as all program text contained between the opening and closing "{" and "}" tokens in the class-body, struct-body, interface-body, or enum-body of the type (including, possibly, types that are nested within the type).

The accessibility domain of a predefined type (such as object, int, or double) is unlimited.

The accessibility domain of a top-level type T declared in a project P is defined as follows:

From these definitions it follows that the accessibility domain of a top-level type is always at least the program text of the project in which the type is declared.

The accessibility domain of a nested member M declared in a type T within a project P is defined as follows (noting that M may itself possibly be a type):

From these definitions it follows that the accessibility domain of a nested member is always at least the program text of the type in which the member is declared. Furthermore, it follows that the accessibility domain of a member is never more inclusive than the accessibility domain of the type in which the member is declared.

In intuitive terms, when a type or member M is accessed, the following steps are evaluated to ensure that the access is permitted:

In the example

public class A
{
   public static int X;
   internal static int Y;
   private static int Z;
}
internal class B
{
   public static int X;
   internal static int Y;
   private static int Z;
   public class C
   {
      public static int X;
      internal static int Y;
      private static int Z;
   }
   private class D
   {
      public static int X;
      internal static int Y;
      private static int Z;
   }
}

the classes and members have the following accessibility domains:

As the example illustrates, the accessibility domain of a member is never larger than that of a containing type. For example, even though all X members have public declared accessibility, all but A.X have accessibility domains that are constrained by a containing type.

As described in §3.2, all members of a base class, except for constructors and destructors, are inherited by derived types. This includes even private members of a base class. However, the accessibility domain of a private member includes only the program text of the type in which the member is declared. In the example

class A
{
   int x;
   static void F(B b) {
      b.x = 1;      // Ok
   }
}
class B: A
{
   static void F(B b) {
      b.x = 1;      // Error, x not accessible
   }
}

the B class inherits the private member x from the A class. Because the member is private, it is only accessible within the class-body of A. Thus, the access to b.x succeeds in the A.F method, but fails in the B.F method.