public class Counter
{
    private Counter() { }
    public static int currentCount;
    public static int IncrementCount()
    {
        return ++currentCount;
    }
}

class TestCounter
{
    static void Main()
    {
        // If you uncomment the following statement, it will generate
        // an error because the constructor is inaccessible:
        // Counter aCounter = new Counter();   // Error

        Counter.currentCount = 100;
        Counter.IncrementCount();
        Console.WriteLine(“New count: {0}”, Counter.currentCount);

        // Keep the console window open in debug mode.
        Console.WriteLine(“Press any key to exit.”);
        Console.ReadKey();
    }
}
// Output: New count: 101

// protected_keyword.cs
using System;
class A
{
    protected int x = 123;
}

class B : A
{
    static void Main()
    {
        A a = new A();
        B b = new B();

        // Error CS1540, because x can only be accessed by
        // classes derived from A.
        // a.x = 10;
       
        // OK, because this class derives from A.
        b.x = 10;  
    }
}

// protected_keyword_2.cs
using System;
class Point
{
    protected int x;
    protected int y;
}

class DerivedPoint: Point
{
    static void Main()
    {
        DerivedPoint dpoint = new DerivedPoint();

        // Direct access to protected members:
        dpoint.x = 10;
        dpoint.y = 15;
        Console.WriteLine(“x = {0}, y = {1}”, dpoint.x, dpoint.y);
    }
}