ECMA-334: 10.8.2 Fully qualified names

Microsoft .NET Framework, ASP.NET, Visual C# (CSharp, C Sharp, C-Sharp) Developer Training, Visual Studio

C# Language Specification

10. Basic concepts 10.8 Namespace and type names 10.8.1 Unqualified name 10.8.2 Fully qualified names

© 2006 ECMA International

10.8.2 Fully qualified names

Every namespace declaration and type declaration has a fully qualified name, which uniquely identifies the namespace or type amongst all others. The fully qualified name of a namespace or type declaration with unqualified name N is determined as follows:

• If the declaration is contained directly in a compilation unit and not nested in any other declaration, its fully qualified name is N.

• Otherwise, its fully qualified name is S.N, where S is the fully qualified name of the immediately enclosing namespace or type declaration.

In other words, the fully qualified name of a declaration is the complete hierarchical path of identifiers (and generic-dimension-specifier (§14.5.11)) that lead to the type or namespace, starting from the global namespace. The fully qualified name of a declaration shall uniquely identify the namespace, non-generic type or generic instance type (§25.1.2) associated with the declaration. It is a compile-time error for the same fully qualified name to refer to two distinct entities. In particular:

• It is an error for both a namespace declaration and a type declaration to have the same fully qualified name.

• It is an error for two different kinds of type declarations to have the same fully qualified name (for example, if both a struct and class declaration have the same fully qualified name).

• It is an error for a type declaration without the partial modifier to have the same fully qualified name as another type declaration (§17.1.4).

[Example: The example below shows several namespace and type declarations along with their associated fully qualified names.

class A {}        // A
namespace X       // X
{
  class B         // X.B
  {
    class C {}    // X.B.C
  }
  namespace Y     // X.Y
  {
    class D {}    // X.Y.D
  }
}
namespace X.Y     // X.Y
{
  class E {}      // X.Y.E
  class G<T>      // X.Y.G<>
  {
    class H {}    // X.Y.G<>.H
  }
  class G<S,T>    // X.Y.G<,>
  {
    class H<U> {} // X.Y.G<,>.H<>
  }
}

end example]