C# 0 The Complete Reference

protected

 access modifier. When a member 

of a class is declared as 

protected

, that member is, with one important exception, private. 

The exception occurs when a protected member is inherited. In this case, a protected member 

of the base class becomes a protected member of the derived class and is, therefore, accessible 

to the derived class. Therefore, by using 

protected

, you can create class members that are 

private to their class but that can still be inherited and accessed by a derived class.

Here is a simple example that uses 

protected

:

// Demonstrate protected.

using System;

class B {

  protected int i, j; // private to B, but accessible by D

  public void Set(int a, int b) {

    i = a;

    j = b;

  }

  public void Show() {

    Console.WriteLine(i + " " + j);

 }

}

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class D : B {

  int k; // private

  // D can access B's i and j

  public void Setk() {

     k = i * j;

  }

  public void Showk() {

    Console.WriteLine(k);

  }

}

class ProtectedDemo {

  static void Main() {

    D ob = new D();

    ob.Set(2, 3); // OK, known to D

    ob.Show();    // OK, known to D

    ob.Setk();  // OK, part of D

    ob.Showk(); // OK, part of D

  }

}

In this example, because