C# access modifier

6. Access modifier in C#
A way to control access to a class and or its members

public
The type or member can be accessed by any other code in the same assembly or another assembly that references it.

private
The type or member can be accessed only by code in the same class or struct.

protected
The type or member can be accessed only by code in the same class, or in a class that is derived from that class.

internal
The type or member can be accessed by any code in the same assembly, but not from another assembly.

protected internal
The type or member can be accessed by any code in the assembly in which it is declared, or from within a derived class in another assembly.

Type Access Modifier

                     | Default   | Permitted declared accessibilities
------------------------------------------------------------------
namespace            | public    | none (always implicitly public)

enum                 | public    | none (always implicitly public)

interface            | internal  | public, internal

class                | internal  | public, internal

struct               | internal  | public, internal

delegate             | internal  | public, internal

Member accesss modifier

                    | Default   | Permitted declared accessibilities
------------------------------------------------------------------
namespace            | public    | none (always implicitly public)

enum                 | public    | none (always implicitly public)

interface            | public    | none

class                | private   | All¹

struct               | private   | public, internal, private²

delegate             | private   | All¹

constructor          | private   | All¹

interface member     | public    | none (always implicitly public)

method               | private   | All¹

field                | private   | All¹

user-defined operator| none      | public (must be declared public)