using System;

public class Program

{

    public static void Main()

    {

        object a = null;

        object b = "l";

        int c = 2;

        b = "lol"+c;

        Console.WriteLine("obj<-->obj: " + ((object)(a) == (object)(b)).ToString());

        Console.WriteLine("str<-->str: " + ((string)(a) == (string)(b)).ToString());

        Console.WriteLine("obj.equals: " + Object.Equals(a,b).ToString());

        Console.WriteLine("obj.ref_equals: " + Object.ReferenceEquals(a,b).ToString());

        Console.WriteLine("a.equals(b): " + (a?.Equals(b)??false).ToString());

    }

}