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Access Modifiers (C# Programming Guide) | Microsoft Docs
Access Modifiers (C# Programming
Guide)
07/20/2015 • 4 minutes to read • Contributors
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In this article
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
1
is declared, or from within a derived class in another assembly.
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:
C#
https://docs.microsoft.com/en-us/dotnet/csharp/programming-guide/classes-and-structs/access-modifiers
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public class Bicycle
{
public void Pedal() { }
}
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.
Class and Struct 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 and Struct Member Accessibility
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.
https://docs.microsoft.com/en-us/dotnet/csharp/programming-guide/classes-and-structs/access-modifiers
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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.
C#
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// 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; }
}
}
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.
Other Types
https://docs.microsoft.com/en-us/dotnet/csharp/programming-guide/classes-and-structs/access-modifiers
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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.
C# Language Specification
For more information, see the C# Language Specification. The language specification is the
definitive source for C# syntax and usage.
See Also
C# Programming Guide
Classes and Structs
Interfaces
private
public
internal
protected
protected internal
private protected
class
struct
interface
https://docs.microsoft.com/en-us/dotnet/csharp/programming-guide/classes-and-structs/access-modifiers
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https://docs.microsoft.com/en-us/dotnet/csharp/programming-guide/classes-and-structs/access-modifiers
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https://docs.microsoft.com/en-us/dotnet/csharp/programming-guide/classes-and-structs/access-modifiers
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https://docs.microsoft.com/en-us/dotnet/csharp/programming-guide/classes-and-structs/access-modifiers
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https://docs.microsoft.com/en-us/dotnet/csharp/programming-guide/classes-and-structs/access-modifiers
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https://docs.microsoft.com/en-us/dotnet/csharp/programming-guide/classes-and-structs/access-modifiers
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https://docs.microsoft.com/en-us/dotnet/csharp/programming-guide/classes-and-structs/access-modifiers
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