How to check input is a valid integer

Question

I try to tell the user that ,whenever he types in a string instead of an integer, he/she should type in a number.But somehow the code within the if statement never shows up.

    private static void Number()
    {
        Console.Write("Type it in a number: ");
        int result = int.Parse(Console.ReadLine());
        if (float.IsNaN(result))
        {
            Console.WriteLine("Please type a number!");
        }
        else
        {
            Console.Write("Hi");
        }
        Console.ReadLine();
    }

1

use `int.TryParse()` – Miguel Sanchez Oct 14 '16 at 05:29

score 4 · Accepted Answer · answered Oct 14 '16 at 05:37

private static void Number()
{
    Console.Write("Type it in a number: ");
    int result;
    bool parsedSuccessfully = int.TryParse(Console.ReadLine(), out result);

    if (parsedSuccessfully == false)
    {
        Console.WriteLine("Please type a number!");
    }
    else
    {
        Console.Write("Hi");
    }
    Console.ReadLine();
}

Mostafiz · Answer 2 · 2016-10-17T09:43:12.257

1

You can do by int.TryParse for that

private static void Number()
    {
        Console.Write("Type it in a number: ");
        int result;
        if (int.TryParse(Console.ReadLine(), out result))
        {
             // user input a valid integer
             // result varaible have the input integer
             Console.Write("Hi");
        }
        else
        {
           // user input none integer
           Console.WriteLine("Please type a number!");
        }
        Console.ReadLine();
    }

edited Oct 17 '16 at 09:43

answered Oct 14 '16 at 05:31

Mostafiz

7,243
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Thank you it worked Mostafiz!:) – Ryepower Oct 14 '16 at 05:38
Thank you for your answers everyone!:) – Ryepower Oct 14 '16 at 05:39
great you are welcome, happy coding :) – Mostafiz Oct 14 '16 at 05:40
@Ryepower what was the problem in answer ? it is always good to avoid variable if no necessary, I have show you the most performatic way without assign a variable(extra memory use) than LittleDebugger's answer – Mostafiz Oct 17 '16 at 09:39

Venkat · Answer 3 · 2021-04-23T12:25:11.860

-1

Try using TryParse method to validate the entered string , you can also use

int.TryParse

Code :

private static void ValidateInput() {

  Console.Write("Type the number: ");
  string userInput = Console.ReadLine();

  int result;
  bool isValidNumber = Int32.TryParse(userInput, out result);

  Console.WriteLine(isValidNumber ? "Hi, You have entered a valid number" : "Entered value is not a vald number, so please type a number!");

  Console.ReadLine();
}

edited Apr 23 '21 at 12:25

answered Oct 14 '16 at 05:32

Venkat

2,549
2
28
61

Thank you Venkat:) – Ryepower Oct 14 '16 at 05:48
2

This code is incorrect and does not parse. – NJH Oct 14 '16 at 05:51
@Ryepower Welcome ! – Venkat Oct 14 '16 at 05:51
@NJH Can you please mention the error in the code , So that I can change? – Venkat Oct 14 '16 at 05:52
1

(isValidNumber)? Console.WriteLine("Please type a number!") : Console.WriteLine("Hi"); – Ryepower Oct 14 '16 at 05:56
1

You are using the ternary expression incorrectly. Additionally, your logic is the wrong way around and would display "Please type a number!" when a valid integer was supplied. – NJH Oct 14 '16 at 05:56
1

This is the part that is underlined in visual basic for me – Ryepower Oct 14 '16 at 05:56
@NJH I will check , Thank you – Venkat Oct 14 '16 at 05:57
@Ryepower - The working code snipper is updated in the answer. Thanks – Venkat Apr 23 '21 at 12:26
@NJH - Thanks, the answer is updated with working code – Venkat Apr 23 '21 at 12:26

How to check input is a valid integer

3 Answers3