using System;

public class Program

{

    class B

    {

        protected int number = 11;

    }

    class A : B

    {

        public string customValue = null;

        public A(){

            Console.WriteLine(this.number); // the protected members can be accessed inside the class who make the inheritance.

            this.customValue = "My custom value "+ this.number.ToString();

        }

    }

    public static void Main()

    {

        A a = new A();

        Console.WriteLine(a.customValue); // And just the public members can be accessed from outside, when you create an instance of some class.

        B b = new B();

        //int testB = b.number; //error inaccessable due to its protection level

    }

}