ECMA-334 C# Language Specification

10.7.1.1: Hiding through nesting

Name hiding through nesting can occur as a result of nesting namespaces or types within namespaces, as a result of nesting types within classes or structs, and as a result of parameter and local variable declarations.

[Example: In the example 
class A  
{  
   int i = 0;  
   void F() {  
      int i = 1;  
   }  
   void G() {  
      i = 1;  
   }  
}
within the F method, the instance variable i is hidden by the local variable i, but within the G method, i still refers to the instance variable. end example]

When a name in an inner scope hides a name in an outer scope, it hides all overloaded occurrences of that name. [Example: In the example 
class Outer  
{  
   static void F(int i) {}  
   static void F(string s) {}  
   class Inner  
   {  
      void G() {  
         F(1);    // Invokes Outer.Inner.F  
         F("Hello");  // Error  
      }  
      static void F(long l) {}  
   }  
}
the call F(1) invokes the F declared in Inner because all outer occurrences of F are hidden by the inner declaration. For the same reason, the call F("Hello") results in a compile-time error. end example]