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Access Modifiers (C# Programming

Guide)

In this article

C# Copy

07/20/2015 • 4 minutes to read • Contributors all

Class and Struct Accessibility

Class and Struct Member Accessibility

Other Types

C# Language Specification

See Also

All types and type members have an accessibility level, which controls whether they can be used

from other code in your assembly or other assemblies. You can use the following access

modifiers to specify the accessibility of a type or member when you declare it:

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.

1

private protected The type or member can be accessed only within its declaring assembly, by

code in the same class or in a type that is derived from that class.

The following examples demonstrate how to specify access modifiers on a type and member:

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public class Bicycle

{

public void Pedal() { }

}

Class and Struct Accessibility

Class and Struct Member Accessibility

Not all access modifiers can be used by all types or members in all contexts, and in some cases

the accessibility of a type member is constrained by the accessibility of its containing type. The

following sections provide more details about accessibility.

Classes and structs that are declared directly within a namespace (in other words, that are not

nested within other classes or structs) can be either public or internal. Internal is the default if no

access modifier is specified.

Struct members, including nested classes and structs, can be declared as public, internal, or

private. Class members, including nested classes and structs, can be public, protected internal,

protected, internal, private protected or private. The access level for class members and struct

members, including nested classes and structs, is private by default. Private nested types are not

accessible from outside the containing type.

Derived classes cannot have greater accessibility than their base types. In other words, you

cannot have a public class B that derives from an internal class A. If this were allowed, it

would have the effect of making A public, because all protected or internal members of A are

accessible from the derived class.

You can enable specific other assemblies to access your internal types by using the

InternalsVisibleToAttribute. For more information, see Friend Assemblies.

Class members (including nested classes and structs) can be declared with any of the six types of

access. Struct members cannot be declared as protected because structs do not support

inheritance.

Normally, the accessibility of a member is not greater than the accessibility of the type that

contains it. However, a public member of an internal class might be accessible from outside the

assembly if the member implements interface methods or overrides virtual methods that are

defined in a public base class.

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C# Copy

// public class:

public class Tricycle

{

// protected method:

protected void Pedal() { }

// private field:

private int wheels = 3;

// protected internal property:

protected internal int Wheels

{

get { return wheels; }

}

}

Other Types

The type of any member that is a field, property, or event must be at least as accessible as the

member itself. Similarly, the return type and the parameter types of any member that is a

method, indexer, or delegate must be at least as accessible as the member itself. For example,

you cannot have a public method M that returns a class C unless C is also public. Likewise,

you cannot have a protected property of type A if A is declared as private.

User-defined operators must always be declared as public. For more information, see operator

(C# Reference).

Finalizers cannot have accessibility modifiers.

To set the access level for a class or struct member, add the appropriate keyword to the member

declaration, as shown in the following example.

Note

The protected internal accessibility level means protected OR internal, not protected AND

internal. In other words, a protected internal member can be accessed from any class in the

same assembly, including derived classes. To limit accessibility to only derived classes in

the same assembly, declare the class itself internal, and declare its members as protected.

Also, starting with C# 7.2, you can use the private protected access modifier to achieve the

same result without need to make the containing class internal.

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C# Language Specification

See Also

Interfaces declared directly within a namespace can be declared as public or internal and, just

like classes and structs, interfaces default to internal access. Interface members are always public

because the purpose of an interface is to enable other types to access a class or struct. No

access modifiers can be applied to interface members.

Enumeration members are always public, and no access modifiers can be applied.

Delegates behave like classes and structs. By default, they have internal access when declared

directly within a namespace, and private access when nested.

For more information, see the C# Language Specification. The language specification is the

definitive source for C# syntax and usage.

C# Programming Guide

Classes and Structs

Interfaces

private

public

internal

protected

protected internal

private protected

class

struct

interface

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