Input string was not in a correct format

Question

I'm new with C#, I have some basic knowledge in Java but I can't get this code to run properly.

It's just a basic calculator, but when I run the program VS2008 gives me this error:

I did almost the same program but in java using JSwing and it worked perfectly.

Here's the form of c#:

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;

namespace calculadorac
{
    public partial class Form1 : Form
    {

    int a, b, c;
    String resultado;

    public Form1()
    {
        InitializeComponent();
        a = Int32.Parse(textBox1.Text);
        b = Int32.Parse(textBox2.Text);
    }

    private void button1_Click(object sender, EventArgs e)
    {
        add();
        result();
    }

    private void button2_Click(object sender, EventArgs e)
    {
        substract();
        result();
    }

    private void button3_Click(object sender, EventArgs e)
    {
        clear();
    }

    private void add()
    {
        c = a + b;
        resultado = Convert.ToString(c);
    }

    private void substract()
    {
        c = a - b;
        resultado = Convert.ToString(c);
    }

    private void result()
    {
        label1.Text = resultado;
    }

    private void clear()
    {
        label1.Text = "";
        textBox1.Text = "";
        textBox2.Text = "";
    }
}

What can be the problem? Is there a way to solve it?

PS: I also tried

a = Convert.ToInt32(textBox1.text);
b = Convert.ToInt32(textBox2.text);

and it didn't work.

Marivaux

Answer 1

The error means that the string you're trying to parse an integer from doesn't actually contain a valid integer.

It's extremely unlikely that the text boxes will contain a valid integer immediately when the form is created - which is where you're getting the integer values. It would make much more sense to update a and b in the button click events (in the same way that you are in the constructor). Also, check out the Int.TryParse method - it's much easier to use if the string might not actually contain an integer - it doesn't throw an exception so it's easier to recover from.

Firebrat

This error message could be thrown also when try to Convert.ToDouble input comming from user with different cultureinfo, so you could use Convert.ToDouble (String, IFormatProvider) instead of just Convert.ToDouble (String). It is hard to debug, because program will work on you system, but will throw error on some of its users, this is why I have a method to log errors on my server and I found out for the problem fastly. – Dira

Answer 2

I ran into this exact exception, except it had nothing to do with parsing numerical inputs. So this isn't an answer to the OP's question, but I think it's acceptable to share the knowledge.

I'd declared a string and was formatting it for use with JQTree which requires curly braces ({}). You have to use doubled curly braces for it to be accepted as a properly formatted string:

string measurements = string.empty;
measurements += string.Format(@"
    {{label: 'Measurement Name: {0}',
        children: [
            {{label: 'Measured Value: {1}'}},
            {{label: 'Min: {2}'}},
            {{label: 'Max: {3}'}},
            {{label: 'Measured String: {4}'}},
            {{label: 'Expected String: {5}'}},
        ]
    }},",
    drv["MeasurementName"] == null ? "NULL" : drv["MeasurementName"],
    drv["MeasuredValue"] == null ? "NULL" : drv["MeasuredValue"],
    drv["Min"] == null ? "NULL" : drv["Min"],
    drv["Max"] == null ? "NULL" : drv["Max"],
    drv["MeasuredString"] == null ? "NULL" : drv["MeasuredString"],
    drv["ExpectedString"] == null ? "NULL" : drv["ExpectedString"]);

Hopefully this will help other folks who find this question but aren't parsing numerical data.

Selfdelusion

How is this a 66 times upvoted answer to the question of how to parse integers in C#? – Devi

@Devi the question is "Input string was not in a correct format". 66 people found it useful, it is relevant too.. Whats the problem ? – Gondi

I'm back again at this answer for at least the second time when googling "input string was not in the correct format". Tried to upvote, but I already had when I first viewed it years ago. – Leyden

Answer 3

If you are not validating explicitly for numbers in the text field, in any case its better to use

int result=0;
if(int.TryParse(textBox1.Text,out result))

Now if the result is success then you can proceed with your calculations.

Obla

Typically result doesn't need to be initialized. – Photoflash

Answer 4

Problems

There are some possible cases why the error occurs:

1. Because textBox1.Text contains only number, but the number is too big/too small

2. Because textBox1.Text contains:

   • a) non-number (except space in the beginning/end, - in the beginning) and/or
   • b) thousand separators in the applied culture for your code without specifying NumberStyles.AllowThousands or you specify NumberStyles.AllowThousands but put wrong thousand separator in the culture and/or
   • c) decimal separator (which should not exist in int parsing)

---

NOT OK Examples:

Case 1

a = Int32.Parse("5000000000"); //5 billions, too large
b = Int32.Parse("-5000000000"); //-5 billions, too small
//The limit for int (32-bit integer) is only from -2,147,483,648 to 2,147,483,647

Case 2 a)

a = Int32.Parse("a189"); //having a 
a = Int32.Parse("1-89"); //having - but not in the beginning
a = Int32.Parse("18 9"); //having space, but not in the beginning or end

Case 2 b)

NumberStyles styles = NumberStyles.AllowThousands;
a = Int32.Parse("1,189"); //not OK, no NumberStyles.AllowThousands
b = Int32.Parse("1,189", styles, new CultureInfo("fr-FR")); //not OK, having NumberStyles.AllowThousands but the culture specified use different thousand separator

Case 2 c)

NumberStyles styles = NumberStyles.AllowDecimalPoint;
a = Int32.Parse("1.189", styles); //wrong, int parse cannot parse decimal point at all!

---

Seemingly NOT OK, but actually OK Examples:

Case 2 a) OK

a = Int32.Parse("-189"); //having - but in the beginning
b = Int32.Parse(" 189 "); //having space, but in the beginning or end

Case 2 b) OK

NumberStyles styles = NumberStyles.AllowThousands;
a = Int32.Parse("1,189", styles); //ok, having NumberStyles.AllowThousands in the correct culture
b = Int32.Parse("1 189", styles, new CultureInfo("fr-FR")); //ok, having NumberStyles.AllowThousands and correct thousand separator is used for "fr-FR" culture

---

Solutions

In all cases, please check the value of textBox1.Text with your Visual Studio debugger and make sure that it has purely-acceptable numerical format for int range. Something like this:

1234

Also, you may consider of

1. using TryParse instead of Parse to ensure that the non-parsed number does not cause you exception problem.

2. check the result of TryParse and handle it if not true

   int val;
   bool result = int.TryParse(textbox1.Text, out val);
   if (!result)
       return; //something has gone wrong
   //OK, continue using val
   

Endearment

Answer 5

You may encounter this exception when you use a string formatter with invalid bracket syntax.

// incorrect
string.Format("str {incorrect}", "replacement")

// correct
string.Format("str {1}", "replacement")

Clop

I had a space in front of my first parameter "{ 0:c2}" which caused it. – Psychometrics

Answer 6

In my case I forgot to put double curly brace to escape. {{myobject}}

Cash

What? How is that an answer to the question? We don't even know what "your case" is... – Devi

@Cash At the time you replied the OP's question was about 7 years old. You need to clarify what exactly your case was, and how putting double curly braces corrected the problem you had. You should also include details about the language that are working with. The OP's question involves c#. Your mention of double curly braces "{{}}" is out of context but strongly suggests that you are working with a different language or templating library which would have no impact or benefit to the OP's scenario. – Chrismatory

Answer 7

You have not mentioned if your textbox have values in design time or now. When form initializes text box may not hae value if you have not put it in textbox when during form design. you can put int value in form design by setting text property in desgin and this should work.

Wives

Answer 8

it was my problem too .. in my case i changed the PERSIAN number to LATIN number and it worked. AND also trime your string before converting.

PersianCalendar pc = new PersianCalendar();
char[] seperator ={'/'};
string[] date = txtSaleDate.Text.Split(seperator);
int a = Convert.ToInt32(Persia.Number.ConvertToLatin(date[0]).Trim());

Thyroiditis

Answer 9

I had a similar problem that I solved with the following technique:

The exception was thrown at the following line of code (see the text decorated with ** below):

static void Main(string[] args)
    {

        double number = 0;
        string numberStr = string.Format("{0:C2}", 100);

        **number = Double.Parse(numberStr);**

        Console.WriteLine("The number is {0}", number);
    }

After a bit of investigating, I realized that the problem was that the formatted string included a dollar sign ($) that the Parse/TryParse methods cannot resolve (i.e. - strip off). So using the Remove(...) method of the string object I changed the line to:

number = Double.Parse(numberStr.Remove(0, 1)); // Remove the "$" from the number

At that point the Parse(...) method worked as expected.

Moltke