using static System.Console;

using System;

public class Program {

    public static void Main() {

        int? x = null;

        int y = 10;

        string z = null; //só como exemplo, não faz sentido converter string p/ string

        try {

            WriteLine($"Convert.ToString(x) = {Convert.ToString(x)}");

            WriteLine($"Convert.ToString(y) = {Convert.ToString(y)}");

            WriteLine($"Convert.ToString(z) = {Convert.ToString(z)}");

            WriteLine($"x.ToString() = {x.ToString()}");

            WriteLine($"y.ToString() = {y.ToString()}");

            WriteLine($"z.ToString() = {z.ToString()}");

        } catch (Exception ex) {

            WriteLine("Falhou");

            WriteLine(ex);

        }

    }

}