Numeric string validation in c#

Question

I'm trying to validate if the 'columnsValidation' is a numeric string, and convert it to an int, if so.

For some reason, I end up in an endless loop, because 'isNumber' always equals false...

This code is part of my lottery project.

I hope that my question is clear enough, if additional information is needed just tell me and I'll answer.

Thanks in advance, Ilan.

Console.WriteLine("Please insert the number of rows: ");

        string columnsValidation = Console.ReadLine();

        bool isNumber = false;

            while(isNumber == false)
            {
                bool.TryParse(columnsValidation, out isNumber);
                if (isNumber == true)
                    columns = int.Parse(columnsValidation);
                else
                {
                    Console.WriteLine("You've inserted an invalid value, please try again.");
                    columnsValidation = Console.ReadLine();
                }
            }

bool.TryParse tries to get a bool out of 'true' or 'false' and tells you nothing about if columsValidaton is a number. — user1064248
– user1064248, Commented Jan 21, 2014 at 18:30
The way you are using bool.TryParse is incorrect. If you aren't going to use it's output, then you might as well use bool.Parse(columnsValidation) — poy
– poy, Commented Jan 21, 2014 at 18:30

Selman Genç · Accepted Answer · 2014-01-21 18:32:00Z

2

You need to use int.TryParse with columnsValidation

if (!int.TryParse(columnsValidation,out columns)
{
     Console.WriteLine("You've inserted an invalid value, please try again.");
     columnsValidation = Console.ReadLine();
}
else
{ 
    isNumber = true;
}

answered Jan 21, 2014 at 18:32

Selman Genç

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Comments

Andrei · Accepted Answer · 2014-01-21 18:29:22Z

2

Correct your usage of TryParse:

isNumber = int.TryParse(columnsValidation, out columns);

TryParse returns boolean indicating whether the parsing succeeded, and in case of success sets out param with the parsing result.

answered Jan 21, 2014 at 18:29

Andrei

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Comments

Muhammad Umar · Accepted Answer · 2014-01-21 18:33:41Z

0

Why not you use Int.TryParse

int columns = 0;

while(true)
{
    if (!Int32.TryParse(columnsValidation,out columns)
    {
        Console.WriteLine("You've inserted an invalid value, please try again.");
        columnsValidation = Console.ReadLine();
    }
    else
    {
        break;
    }
}

answered Jan 21, 2014 at 18:33

Muhammad Umar

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