var names = new[] {"Foo","Bar","Fizz","Buzz"};

var thirdName = names.ElementAtOrDefault(2);
Console.WriteLine(thirdName); //Fizz

var minusOnethName = names.ElementAtOrDefault(-1);
Console.WriteLine(minusOnethName); //null

var fifthName = names.ElementAtOrDefault(4);
Console.WriteLine(fifthName); //null