System.FormatException: Input string was not in a correct format from an int.Parse

Question

try
{
    for (int i = 0; i < 4; i++)
    {
        playerGuess[i] = int.Parse(Console.ReadLine()); //says this is the error
    }
}
catch (Exception ex)
{
    Console.WriteLine("{0} Exception caught", ex);
    Console.Read();
}

I run this code, and for some reason, it outputs the following errors:

   at System.Number.ThrowOverflowOrFormatException(ParsingStatus status, TypeCode type)
   at System.Number.ParseInt32(ReadOnlySpan`1 value, NumberStyles styles, NumberFormatInfo info)
   at System.Convert.ToInt32(String value)

I tried fixes I've seen on another thread like this, but I can't get them to work. any ideas?

@urlreader I didn't input anything, it prompted these errors before I could do anything. — Delirium
– Delirium, Commented Apr 26, 2020 at 21:32

Adam · Accepted Answer · 2020-04-26 21:34:21Z

3

int.Parse() will fail with that exception if the value you provide it is not capable of being converted to an int, and as written you have no checks on the string being read from the console to verify that is the case before passing it to the method.

You can use int.TryParse() instead, which gives you a bit more control over how to handle a failure by returning a boolean indicating success. You might present an error message instead, and ask the user to resubmit.

string input = Console.ReadLine();
int result;

if(int.TryParse(input, out result)) // TryParse returns a boolean showing whether the parse worked
{
   // then perform your behavior safely
}

answered Apr 26, 2020 at 21:34

Adam

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