A type-declaration is a class-declaration (17.1), a struct-declaration (18.1), an interface-declaration (20.1), an enum-declaration (21.1), or a delegate-declaration (22.1).

type-declaration

class-declaration

struct-declaration

interface-declaration

enum-declaration

delegate-declaration

A type-declaration can occur as a top-level declaration in a compilation unit or as a member declaration within a namespace, class, or struct.

When a type declaration for a type T occurs as a top-level declaration in a compilation unit, the fully qualified name of the newly declared type is simply T. When a type declaration for a type T occurs within a namespace, class, or struct, the fully qualified name of the newly declared type is N.T, where N is the fully qualified name of the containing namespace, class, or struct.

A type declared within a class or struct is called a nested type (17.2.6).

The permitted access modifiers and the default access for a type declaration depend on the context in which the declaration takes place (10.5.1):

• Types declared in compilation units or namespaces can have public or internal access. The default is internal access.
• Types declared in classes can have public, protected internal, protected, internal, or private access. The default is private access.
• Types declared in structs can have public, internal, or private access. The default is private access.