Not able to cast string to int. Error msg: Input string was not in a correct format

Question

I havethe following code which outputs the number '40':

Hashtable ht = new Hashtable();
ht.Add("numRooms", pageData.Property["romtotalt"].ToString());
string str = ht["numRooms"].ToString();
lblMigrate.Text = i.ToString();

Then I try to convert the string to an int, and I get an exception / error:

Hashtable ht = new Hashtable();
ht.Add("numRooms", pageData.Property["romtotalt"].ToString());
string str = ht["numRooms"].ToString();
int i = Convert.ToInt32(str);  // <-- This is where it fails I t hink. But why??
lblMigrate.Text = i.ToString();

This is the error message I get:

Server Error in '/' Application.
Input string was not in a correct format.
Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.FormatException: Input string was not in a correct format.

Source Error:

An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.

Stack Trace:

[FormatException: Input string was not in a correct format.]
   System.Number.StringToNumber(String str, NumberStyles options, NumberBuffer& number, NumberFormatInfo info, Boolean parseDecimal) +7469351
   System.Number.ParseInt32(String s, NumberStyles style, NumberFormatInfo info) +119
   development.templates.HotellGuide.btnMigrateHotels_Click(Object sender, EventArgs e) +956
   System.Web.UI.WebControls.Button.OnClick(EventArgs e) +111
   System.Web.UI.WebControls.Button.RaisePostBackEvent(String eventArgument) +110
   System.Web.UI.WebControls.Button.System.Web.UI.IPostBackEventHandler.RaisePostBackEvent(String eventArgument) +10
   System.Web.UI.Page.RaisePostBackEvent(IPostBackEventHandler sourceControl, String eventArgument) +13
   System.Web.UI.Page.RaisePostBackEvent(NameValueCollection postData) +36
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +1565


Version Information: Microsoft .NET Framework Version:2.0.50727.3082; ASP.NET Version:2.0.50727.3082

I don't understand what's wrong. I'va castet string to int multiple times before, and never has this problem occured.

Please help :)

Update

I have found a solution. I have NO idea why this works.... but it works...
I put the convertion inside a Try Catch, and now it works. Figure that one out :op

int numRooms = 0;
int numAllergyRooms = 0;

try
{
    numRooms = Convert.ToInt32(newHotel["numRooms"].ToString().Trim());
    numAllergyRooms = Convert.ToInt32(newHotel["numAllergyRooms"].ToString().Trim());
}
catch (Exception ex)
{
    Console.WriteLine("{0} Exception caught.", ex);
}

Also spoken of as Casting ;o) blogs.msdn.com/csharpfaq/archive/2004/05/30/144652.aspx. I know propert casting is eg. (Int23)myString - but if that doesnt work, you either must pars or convert. — Steven
– Steven, Commented Aug 27, 2009 at 8:32
I think you should debug your app, try to use showmessage to see the str before converting. — Wael Dalloul
– Wael Dalloul, Commented Aug 27, 2009 at 9:29

zweihander · Accepted Answer · 2009-08-27 08:24:37Z

9

I think the line "Input string was not in a correct format" explains it all. In the line

 int i = Convert.ToInt32(str);

str might be containing alphabetic characters. Take a look at it while debugging, what does it contain?

answered Aug 27, 2009 at 8:24

zweihander

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2 Comments

Steven Over a year ago

I'm using Visual Web Developer 2008 and I haven't been able to make the debugging work :( The input string only contains the number '40' and maybe white space. Therefor I don't understand what it merans by 'incorrect format'

Michael Stum Over a year ago

"and maybe white space" <-- Then you better use str.Trim(), because if you maybe have white space then maybe that will crash the function.

Mohammad Motaghi · Accepted Answer · 2011-01-29 16:46:35Z

4

I had the same problem but only try catch method solved my problem

        try
        {
            decimal dPrice=Convert.ToDecimal(sPrice);
            decimal dFreight = Convert.ToDecimal(sFreight);
            decimal dLocalship = Convert.ToDecimal(sLocalship);
            decimal dTarrif = Convert.ToDecimal(sTarrif);
            decimal dBenefit = Convert.ToDecimal(sBenefit);
            decimal dTax = Convert.ToDecimal(sTax);
            decimal dVat = Convert.ToDecimal(sVat);
            decimal dConv = Convert.ToDecimal(sConv);
            decimal factors=(dTarrif+dBenefit+dTax+dVat)/100+1;
            decimal dTotal=(dPrice+dFreight)*dConv;
            dTotal=dTotal*factors;
            string st = Convert.ToString(dTotal);
            e.Row.Cells[iCell].Text = "price is: " + st + " Rials";
        }
        catch(Exception ex)
        {
            Console.WriteLine("{0} Exception caught.", ex);
        }

answered Jan 29, 2011 at 16:46

Mohammad Motaghi

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1 Comment

Christopher Bonitz Over a year ago

Same problem, only a try catch works, checked for all possible combination of characters i can think of, newlines, spaces...

Seb Nilsson · Accepted Answer · 2009-08-27 08:47:17Z

2

You should add Trim() to your code-line where you think it fails. It probably has to do with excessive spaces.

int i = Convert.ToInt32(str.Trim());

Maybe even check to see if str is string.Empty, this will also cause Convert.ToInt32 to crash.

if (string.IsNullOrEmpty(str)) {
    str = "0";
}

edited Aug 27, 2009 at 8:47

answered Aug 27, 2009 at 8:39

Seb Nilsson

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4 Comments

Steven Over a year ago

The string is not empty, it contains the number '40'. Also adding Trim() dfoes not help.

LukeH Over a year ago

@Steven: Convert.ToInt32 will work if the string contains just the two characters "40" and nothing else.

Steven Over a year ago

@Luke: Normally yes. But in this case, no. See my solution.

LukeH Over a year ago

@Steven: It looks like your "solution" is just burying the error in a try...catch, rather than preventing it.

Wael Dalloul · Accepted Answer · 2009-08-27 08:33:36Z

1

The code is ok, but if the str may have white space, so you should remove them before convert:

int i = Convert.ToInt32(str.Replace(" " ,""));  // <-- This is where it fails I t hink. But why??

answered Aug 27, 2009 at 8:33

Wael Dalloul

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1 Comment

Steven Over a year ago

Addin Trim() does not help. Whitespace is not the problem.

Cthulhu · Accepted Answer · 2015-12-29 17:45:12Z

0

It will be that you are trying to convert Nulls or in this case "" (after your .ToString()) to an int.

Try something that will insert an acceptable placeholder for nulls such as -1 shown in the code below.

Convert.ToInt32(newHotel["numAllergyRooms"].ToString().Trim() == "" ? "-1" : newHotel["numAllergyRooms"].ToString().Trim());

edited Dec 29, 2015 at 17:45

Cthulhu

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answered Dec 29, 2015 at 17:04

gazma

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Comments

Ronny D'Hoore · Accepted Answer · 2019-02-01 11:48:23Z

0

The cause might also be a registry problem. See https://support.microsoft.com/en-us/help/942460/system-formatexception-occurs-when-attempting-to-convert-a-numeric-str

They explain that a proper number string might still fail to convert if the value HKEY_CURRENT_USER\Control Panel\International\sPositiveSign contains something bad. In our parts of the world, the value for this key should be empty (no space, just empty).

Probably that was not your problem, but I'm adding it here for someone who might be having exactly this as the cause for their problem...

answered Feb 1, 2019 at 11:48

Ronny D'Hoore

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Comments

Larry · Accepted Answer · 2024-12-21 04:17:20Z

0

I found that the error was caused by having a comma in the number, so you can't convert "1,000" to INT, but "1000" is accepted.

answered Dec 21, 2024 at 4:17

Larry

91 bronze badge

1 Comment

Jay Buckman Dec 23, 2024 at 12:00

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