My enum is not a class or namespace

The syntax MyEnum::SomethingElse is a Microsoft extension. It happens to be one I like, but it’s not Standard C++. enum values are added to the surrounding namespace:

 // header
 enum MyEnum {Something = 0, SomethingElse = 1};

 class MyClass {

 MyEnum enumInstance;
 void Foo();

 }

 // implementation
 #include "MyClass.h"

 void Foo() {
     enumInstance = SomethingElse;
 }