C# Tutorial P14 - Do while loop

[Admin]

using System;
class Program
{
    static void Main()
    {
        string UserChoice = ""; // string UserChoice = string.Empty      
        do
        {    
            Console.WriteLine("Please enter your target?");
            int UserTarget = int.Parse(Console.ReadLine());

            int Start = 0;

            while (Start <= UserTarget)
            {
                Console.Write(Start + " ");
                Start = Start + 2;
            }
            
            do
            {
                Console.WriteLine("Do you want to continue - Yes or No?");

                UserChoice = Console.ReadLine().ToUpper();
                if (UserChoice != "YES" && UserChoice != "NO")
                    {
                        Console.WriteLine("Invalid Choice, please say Yes or No");
                    }
            } while (UserChoice != "YES" && UserChoice != "NO");
        } while (UserChoice == "YES");
    }
}

using System;
class Program
{
    static void Main()
    {
        int TotalCoffeeCost = 0;
        string UserDecision = string.Empty;
        do
        {
            int UserChoice = -1
            do
            {
                Console.WriteLine("Please select your coffee size: 1 - Small, 2 - Medium, 3 - Large");
                UserChoice = int.Parse(Console.ReadLine());

                switch (UserChoice)
                {
                    case 1:
                        TotalCoffeeCost += 1;
                        break;
                    case 2:
                        TotalCoffeeCost += 2;
                        break;
                    case 3:
                        TotalCoffeeCost += 3;
                        break;
                    default:
                        Console.WriteLine("Your choice {0} is invalid", UserChoice);
                        break;
                }
            } while (UserChoice != 1 && UserChoice != 2 && UserChoice != 3);

            do
            {
                Console.WriteLine("Do you want to buy another coffee - Yes or No?");
                UserDecision = Console.ReadLine().ToUpper();

                if (UserDecision != "YES" && UserDecision != "NO")
                {
                    Console.WriteLine("Your choice {0} is invalid. Please try again...", UserDecision);
                }
            } while (UserDecision != "YES" && UserDecision != "NO");
        } while (UserDecision.ToUpper() != "NO"

        Console.WriteLine("Thank you for shopping with us");
        Console.WriteLine("Bill Amount = {0}", TotalCoffeeCost);
    }
}