using System;

var first = "A";
var second = "B";
var third = new string(new [] {'A'});

var areEqual = first == second;
//areEqual is false
Console.WriteLine(areEqual);

var areNotEqual = first != second;
//areNotEqual is true
Console.WriteLine(areNotEqual);

areEqual = first == third;
//areEqual is true
Console.WriteLine(areEqual);