c#中各成员默认的可访问性

Depending on the context in which a member declaration takes place, only certain types of declared accessibility are permitted. Furthermore, when a member declaration does not include any access modifiers, the context in which the declaration takes place determines the default declared accessibility.

成员种类	默认可访问性	可以选择的可访问性	书写惯例及示例
Namespaces	public	无	不容许写
Class	private	public/protect/internal/Protected internal/private/	public class
Types	private	public or internal	省略,如 int x;
Struct	private	public, internal, or private	public struct a;
Interface	public	无	不容许写
Enumeration	public	无	不容许写

• Namespaces implicitly have public declared accessibility. No access modifiers are allowed on namespace declarations.
• Types declared in compilation units or namespaces can have public or internal declared accessibility and default to internal declared accessibility.
• Class members can have any of the five kinds of declared accessibility and default to private declared accessibility. (Note that a type declared as a member of a class can have any of the five kinds of declared accessibility, whereas a type declared as a member of a namespace can have only public or internal declared accessibility.)
• Struct members can have public, internal, or private declared accessibility and default to private declared accessibility because structs are implicitly sealed. Struct members introduced in a struct (that is, not inherited by that struct) cannot have protected or protected internal declared accessibility. (Note that a type declared as a member of a struct can have public, internal, or private declared accessibility, whereas a type declared as a member of a namespace can have only public or internal declared accessibility.)
• Interface members implicitly have public declared accessibility. No access modifiers are allowed on interface member declarations.
• Enumeration members implicitly have public declared accessibility. No access modifiers are allowed on enumeration member declarations.