using System;

public class Program

{

    public static void Main()

    {

        ClassA.StaticDo();

        Console.WriteLine("class val: " + ClassA.classVal);

        var instanceA = new ClassA();

        Console.WriteLine("instance A val: " + instanceA.instanceVal);

​

        var instanceB = new ClassA();

        Console.WriteLine("instance B val: " + instanceB.instanceVal);

        var instanceC = new ClassA();

        Console.WriteLine("instance C val: " + instanceC.instanceVal);

        var instanceD = new ClassA();

        Console.WriteLine("instance D val: " + instanceD.instanceVal);

        instanceA.Do();

        instanceB.Do();

        instanceC.Do();

        instanceD.Do();

        Console.WriteLine("class val: " + ClassA.classVal);

        //Console.WriteLine("instance val: " + instanceA.instanceVal);

    }

}

​

public class ClassA 

{

    public static int classVal = 1;

    public int instanceVal = 1;

    public static void StaticDo()

    {

        classVal++;

    }

    public void Do() 

    {

        classVal++;

        this.instanceVal++;

    }

}