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C# C# Basics (Retired) Perfect Final

Seems fine when run in Workspace Mono but test environment states System.ArgumentNullException...

I am on the C# final exam and it requires me to find out the number of times the user would like me to print "yay!" to the screen. I am to ensure their response is valid and a whole number.

Works in Mono but not in the test environment. What am I doing wrong?

Program.cs
using System;

namespace Treehouse.CodeChallenges
{
    class Program
    {
        static void Main()
        {
            bool persist = true;
            var cycles = 0;

            while (persist)
            {
              Console.WriteLine("Enter the number of times to print \"Yay!\": ");
              var reply = Console.ReadLine();
              try
              {
                cycles = int.Parse(reply);

                if (cycles <= 0) 
                {
                  Console.WriteLine(cycles + " is not an acceptable value.");
                  continue;
                }
                else
                {
                persist = false;
                }
              }
              catch(FormatException)
              {
                Console.WriteLine("You must enter a whole number.");
                continue;
              }
            }
            for (int count = 0; count < cycles; count++)
            {
              Console.WriteLine("Yay!");
            }
        }
    }
}

2 Answers

Hi Daniel,

I've updated your code to make it pass:

using System;

namespace Treehouse.CodeChallenges
{
    class Program
    {
        static void Main()
        {
//            bool persist = true;
            var cycles = 0;

//            while (persist)
//            {
              Console.WriteLine("Enter the number of times to print \"Yay!\": ");
              var reply = Console.ReadLine();
              try
              {
                cycles = int.Parse(reply);

                if (cycles <= 0) 
                {
//                  Console.WriteLine(cycles + " is not an acceptable value.");
                    Console.WriteLine("You must enter a positive number.");
//                  continue;
                }
//                else
//                {
//                persist = false;
//                }
              }
              catch(FormatException)
              {
                Console.WriteLine("You must enter a whole number.");
//                continue;
              }
//            }
            for (int count = 0; count < cycles; count++)
            {
              Console.WriteLine("Yay!");
            }
        }
    }
}

I commented out all of the code relating to your while loop and changed one of the writelines.

Firstly your code did work when I was testing it out in a C# workspace. So I can't tell you exactly what the condition was that was causing the error that you were seeing. But what I can tell you is:

  1. You must use the exact wording in the WriteLines that they asked you to. Your use of 'cycles + " is not an acceptable value."' would have caused it to fail the test.

  2. What ever mechanism is running the test in the background is not expecting a while loop in this answer. Time and time again people use a while loop because you have seen it used in the videos for something very similar. But I have not seen an answer that uses a loop pass the test. So I have commented out all of the code relating to the while loop.

I hope that helps a little.

--

Going a little off topic now but I am interested and I have seen this come up quite a few times. Jeremy McLain can a loop be used in this challenge and pass the test? The code:

using System;

namespace Treehouse.CodeChallenges
{
    class Program
    {
        static void Main()
        {
            int cycles;
            String reply;

            while(true){
              Console.Write("Enter the number of times to print \"Yay!\": ");
              reply = Console.ReadLine();
              try {
                cycles = int.Parse(reply);
                for (int count = 0; count < cycles; count++){
                  Console.WriteLine("Yay!");
                }
                break;
              }
              catch(FormatException) {
                Console.WriteLine("You must enter a whole number.");
              }
            }
        }
    }
}

Will pass task 1, but on task 2 generates the same error that Daniel was getting:

System.ArgumentNullException: Value cannot be null.
Parameter name: String
  at System.Number.StringToNumber (System.String str, NumberStyles options, System.NumberBuffer& number, System.Globalization.NumberFormatInfo info, Boolean parseDecimal) [0x00054] in /builddir/build/BUILD/mono-4.2.1/external/referencesource/mscorlib/system/number.cs:1080 
  at System.Number.ParseInt32 (System.String s, NumberStyles style, System.Globalization.NumberFormatInfo info) [0x00014] in /builddir/build/BUILD/mono-4.2.1/external/referencesource/mscorlib/system/number.cs:751 
  at System.Int32.Parse (System.String s) [0x00000] in /builddir/build/BUILD/mono-4.2.1/external/referencesource/mscorlib/system/int32.cs:140 
  at Treehouse.CodeChallenges.Program.Main () <0x40bff830 + 0x00056> in :0 
  at MonoTester.Run () [0x00197] in MonoTester.cs:124 
  at MonoTester.Main (System.String[] args) [0x00013] in MonoTester.cs:27

Running the same code in a Workspace seems to happily work when the input is:

treehouse:~/workspaces$ mono Program.exe
Enter the number of times to print "Yay!: 2
Yay!
Yay!
treehouse:~/workspaces$ mono Program.exe
Enter the number of times to print "Yay!:
You must enter a whole number.
Enter the number of times to print "Yay!: 1.1
You must enter a whole number.
Enter the number of times to print "Yay!: -1
treehouse:~/workspaces$ mono Program.exe
Enter the number of times to print "Yay!: test
You must enter a whole number.
Enter the number of times to print "Yay!: -1.1
You must enter a whole number.

So the code works with a null entry, 1, 1.1 -1, -1.1 and text .... so what is causing the task to fail?

Hey thank you for your validation on my code. I thought it was a bug in the test environment. Glad I am not going crazy. =)

Danielle Gonsalves
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Danielle Gonsalves
Full Stack JavaScript Techdegree Graduate 21,324 Points

Hello! I was also having this problem. After doing some research on the msdn, I found out that the Console.ReadLine(); was returning null, getting the same exception. My fix was to check for null. Here's what I did:

using System;

namespace Treehouse.CodeChallenges
{
    class Program
    {
        static void Main()
        {
            int number;
            int i = 0;

            while(true)
            {
              Console.Write("Enter the number of times to print \"Yay!\": ");
              string entry = Console.ReadLine();

   //           if (entry == null)
   //           {
   //            break; 
   //          }

              try
              {
                number = int.Parse(entry);            

                while (i < number)
                {
                    i += 1;
                    Console.WriteLine("Yay!");
                }
                break;
              }
              catch(FormatException)
              {
                Console.WriteLine("You must enter a whole number.");
                continue;
              }
            }
        } 
    }
}

I commented out my null check. After inserting that, it passed the test. This is the msdn article I found, at the second bullet point: Link I believe my problem was that the test environment was redirecting the console from a file, since it worked in Workspaces before adding the null check.