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C# C# Basics (Retired) Perfect Final

Posted by tung nguyen
tung nguyen
Courses Plus Student 1,666 Points

FormatException

i have this err. and i dont know how to fix it. pls help me 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 () [0x00011] in <63c0b697f8714d7dadfbc9d3af622980>:0 at MonoTester.Run () [0x00208] in /workdir/MonoTester.cs:140

Program.cs 
using System;

namespace Treehouse.CodeChallenges
{
    class Program
    {
        static void Main()
        {
            int i = 0;
            while(true)
            try {
                    Console.Write("Enter the number of times to print \"Yay!\": ");
                    int number = int.Parse(Console.ReadLine());
                    while (i < number)
                    { Console.WriteLine("\"Yay!\""); i++; }
                    break;

                }

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

        }
    }
}

2 Answers

Richard Schwind
Richard Schwind
1,785 Points
Richard Schwind
Richard Schwind
1,785 Points

Try using:

int number = Convert.ToInt32(Console.ReadLine());

Instead of:

int number = int.Parse(Console.ReadLine());

int.Parse() throws an ArgumentNullException when it is passed a null argument. However, Convert.ToInt32() returns 0 when it is passed a null argument. For a more in-depth explanation on how these two methods work, check out this discussion on StackOverflow.

tung nguyen
PLUS
tung nguyen
Courses Plus Student 1,666 Points
tung nguyen
tung nguyen
Courses Plus Student 1,666 Points

oh i see, thank you so much ^^