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C#

Dominik Huber
Dominik Huber
4,631 Points
Posted by Dominik Huber
Dominik Huber
4,631 Points

My variable gets set to null somehow - can you please help me?

I tried and tried but I can't get it to work and I don't know why. The Error message I got is this: " Bummer! System.ArgumentNullException: Value cannot be null. Parameter name: String. See output for stack trace."

So anyhow the count = int.Parse(Console.ReadLine()); (the one in the if block) gets null assigned, am I right? Why?

The closest I can get to is that code: (Output from Stacktrace at the bottom) /edit: Funny thing. The exact same code in Visual Studio works as intended. Tested it with a positive number, a negative number and zero. All 3 worked just as intended. What am I missing? 

using System;

namespace Treehouse.CodeChallenges
{
    class Program
    {
        static void Main()
        {
            Console.Write("Enter the number of times to print \"Yay!\": ");



            try 
            {
                int loopcount = 0;
                int count = int.Parse(Console.ReadLine());




                while (true) 
                {

                     if (count < 0) 
                     {
                        Console.WriteLine("You must enter a positive number.");
                         count = int.Parse(Console.ReadLine());
                         continue;

                     }

                    if (loopcount < count){
                        Console.WriteLine("Yay!");
                        loopcount += 1;
                    } else {
                        break;
                    }




                }
            }

            catch (FormatException)
            {
                Console.WriteLine("You must enter a whole number.");   
            }




        }
    }
}

System.ArgumentNullException: Value cannot be null.
Parameter name: String
  at System.Number.StringToNumber (System.String str, System.Globalization.NumberStyles options, System.Number+NumberBuffer& number, System.Globalization.NumberFormatInfo info, System.Boolean parseDecimal) [0x00054] in /builddir/build/BUILD/mono-4.8.1/mcs/class/referencesource/mscorlib/system/number.cs:1074 
  at System.Number.ParseInt32 (System.String s, System.Globalization.NumberStyles style, System.Globalization.NumberFormatInfo info) [0x00014] in /builddir/build/BUILD/mono-4.8.1/mcs/class/referencesource/mscorlib/system/number.cs:745 
  at System.Int32.Parse (System.String s) [0x00000] in /builddir/build/BUILD/mono-4.8.1/mcs/class/referencesource/mscorlib/system/int32.cs:120 
  at Treehouse.CodeChallenges.Program.Main () [0x0002d] in <7443b08c0fed4b718a9bdc724518d483>:0 
  at MonoTester.Run () [0x002b3] in MonoTester.cs:169 
  at MonoTester.Main (System.String[] args) [0x00013] in MonoTester.cs:28

1 Answer

Dominik Huber
Dominik Huber
4,631 Points
Dominik Huber
Dominik Huber
4,631 Points

Hi I could solve this issue with a int.TryParse() method. Because the problem was if the user enters nothing - so he just clicks enter when the Console.ReadLine() pops up. I handled that with TryParse().

Thank you anyway for your help :)

Henrik Christensen
seal-mask
.a{fill-rule:evenodd;}techdegree
Henrik Christensen
Python Web Development Techdegree Student 38,322 Points
Henrik Christensen
.a{fill-rule:evenodd;}techdegree
Henrik Christensen
Python Web Development Techdegree Student 38,322 Points

Yeah that was my thought, that the user might hit enter without entering anything => then it would throw that exception - but good you fixed it yourself :-)

Happy coding! :-D