The manifest module, of which there can only be one per assembly, includes the .assembly directive. To export a type defined in any other module of an assembly requires an entry in the assembly's manifest. The following grammar is used to construct such an entry in the manifest:
| Decl ::= | Clause |
|---|---|
.class extern ExportAttr DottedName '{' ExternClassDecl* '}' |
|
| | … |
| ExternClassDecl ::= | Clause |
|---|---|
.file DottedName |
| ExternClassDecl ::= | Clause |
|---|---|
| .class extern DottedName |
|
| .custom CustomDecl |
§II.21 |
The ExportAttr value shall be either public or nested public and shall match the visibility of the type.
For example, suppose an assembly consists of two modules, A.EXE and B.DLL. A.EXE contains the manifest. A public class Foo is defined in B.DLL. In order to export it—that is, to make it visible by, and usable from, other assemblies—a .class extern directive shall be included in A.EXE. Conversely, a public class Bar defined in A.EXE does not need any .class extern directive.
[Rationale: Tools should be able to retrieve a single module, the manifest module, to determine the complete set of types defined by the assembly. Therefore, information from other modules within the assembly is replicated in the manifest module. By convention, the manifest module is also known as the assembly. end rationale]