protected internal (C# Reference)

The protected internal keyword combination is a member access modifier. A protected internal member is accessible from the current assembly or from types that are derived from the containing class. For a comparison of protected internal with the other access modifiers, see Accessibility Levels.


A protected internal member of a base class is accessible from any type within its containing assembly. It is also accessible in a derived class located in another assembly only if the access occurs through a variable of the derived class type. For example, consider the following code segment:

// Assembly1.cs  
// Compile with: /target:library  
public class BaseClass   
   protected internal int myValue = 0;  

class TestAccess 
    void Access()
        BaseClass baseObject = new BaseClass();
        baseObject.myValue = 5;
// Assembly2.cs  
// Compile with: /reference:Assembly1.dll  
class DerivedClass : BaseClass   
    static void Main()
        BaseClass baseObject = new BaseClass();
        DerivedClass derivedObject = new DerivedClass();

        // Error CS1540, because myValue can only be accessed by
        // classes derived from BaseClass.
        // baseObject.myValue = 10; 

        // OK, because this class derives from BaseClass.
        derivedObject.myValue = 10;

This example contains two files, Assembly1.cs and Assembly2.cs. The first file contains a public base class, BaseClass, and another class, TestAccess. BaseClass owns a protected internal member, myValue, which is accessed by the TestAccess type. In the second file, an attempt to access myValue through an instance of BaseClass will produce an error, while an access to this member through an instance of a derived class, DerivedClass will succeed.

Struct members cannot be protected internal because the struct cannot be inherited.

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# Reference
C# Programming Guide
C# Keywords
Access Modifiers
Accessibility Levels
Security concerns for internal virtual keywords