Access Modifiers

Example

In the following example, two classes are declared, CClass1 and CClass2. The public members x and y of the CClass1 are accessed directly from CClass2.

// protected_public.cs

// Public access

using System;
class CClass1 
{
   public int x; 
   public int y;
}

class CClass2 
{
   public static void Main() 
   {
      CClass1 CC = new CClass1();

      // here is direct access to public members:

      CC.x = 3;
      CC.y = 5;
      Console.WriteLine("x = {0}, y = {1}", CC.x, CC.y); 
   }
}

Output

x = 3, y = 5

If you want to change the public access level to private or protected, you will get the error message:

'CClass1.y' is inaccessible due to its protection level.

A protected member of a base class is accessible in a derived class only if the access takes place through the derived class type. For example, consider the following code segment:

class XX 
{
   protected int x = 111;
}

class YY : XX 
{
   void F() 
   {
      XX a = new XX();  
      YY b = new YY();  
      a.x = 7;   // Will give an error

      b.x = 7;   // OK

   }
}

The statement a.x=7 generates an error because XX is not derived from YY.

Note: "Struct members cannot be protected because the struct cannot be inherited."

It is an error to reference a protected member from a class, which is not derived from the protected member's class.

Example

In this example, the class DerivedClass is derived from CClass; therefore, you can access the protected members of the base class directly from the derived class.

// protected_keyword.cs

using System;
class CClass 
{
   protected int a; 
   protected int b;
}

class DerivedClass: CClass 
{
   public static void Main() 
   {
      DerivedClass dC = new DerivedClass();

      //here is direct access to protected members:

      dC.a = 3;
      dC.b = 5;
      Console.WriteLine("a = {0}, b = {1}", dC.a, dC.b); 
   }
}

Output

a = 3, b = 5

If you change the access levels of x and y to private, the compiler will issue the error messages:

'CClass.a' is inaccessible due to its protection level.
'CClass.b' is inaccessible due to its protection level.

It is an error to reference a member with internal access outside the assembly within which it was defined.

Note: An internal virtual method can be overridden in some languages, such as textual Microsoft intermediate language (MSIL) using Ilasm.exe, even though it cannot be overridden using C#.

Example

This example contains two files, Assembly1.cs and Assembly2.cs. The first file contains an internal base class, BaseClass. In the second file, an attempt to access the member of the base class will produce an error.

File Assembly1.cs:

// Assembly1.cs

// compile with: /target:library

internal class BaseClass 
{
public static int IntM = 0;
}

File Assembly2.cs

// Assembly2.cs

// compile with: /reference:Assembly1.dll

// CS0122 expected

class TestAccess 
{
   public static void Main() 
   {
      BaseClass myBase = new BaseClass();   // error, BaseClass not visible outside assembly

   }
}

Nested types in the same body can also access those private members.

It is a compile-time error to reference a private member outside the class or the struct in which it is declared.

Example

In this example, the Emp class contains a public member, Name, and a private member, Salary. The public member can be accessed directly, while the private member must be accessed through the public method GetSalary().

// private_keyword.cs

using System;
class Emp 
{
   public string name = "xx";
   double salary = 100.00;   // private access by default

   public double GetSalary() {
      return salary;
   }
}

class MainClass 
{
   public static void Main() 
   {
      Emp e = new Emp();

      // Accessing the public field:

      string n = e.name; 
      
      // Accessing the private field:

      double s = e.GetSalary();    
   }
}

In the preceding example, if you attempt to access the private members directly by using a statement like this:

double s = e.salary;

you will get the error message:

'Emp.Salary' is inaccessible due to its protection level.