A = double.Parse(ABox.Text);
B = double.Parse(BBox.Text);
C = double.Parse(CBox.Text);
a = double.Parse(a_Box.Text);
b = double.Parse(b_Box.Text);
c = double.Parse(c_Box.Text);
Every time this code is run in my system, it throws an Formatting exception. The textBoxes are empty when the error appears, do they have to have at least a zero in them?
Yes
(An empty string can't be parsed into a double)
Instead of Parse you can consider using TryParse:
double number;
if (Double.TryParse(ABox.Text, out number))
{
...
}
else
{
...
}
Yes. Parse will throw an exception if the input is an empty string. You'll either need to check first whether the textbox is empty before parsing it or you can use TryParse.
Related
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.
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.
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.
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.
Problems
There are some possible cases why the error occurs:
Because textBox1.Text contains only number, but the number is too big/too small
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
using TryParse instead of Parse to ensure that the non-parsed number does not cause you exception problem.
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
In my case I forgot to put double curly brace to escape. {{myobject}}
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")
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.
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());
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.
I built the below code, trying to convert reader[BalanceAmt] to a currency, i.e. $23,456.78. I can't seem to get it to work. It's still returning "23456.782" Any ideas?
while (reader.Read())
{
string MyNum = reader["BalanceAmt"].ToString();
String.Format("{0:#,###0}", MyNum);
BalanceBox.Text = (MyNum);
}
If reader["BalanceAmt"] returns a string then to get your numeric formatting to work, you need to convert it into a number before converting it to currency - i.e.
var myNum = Convert.ToDecimal(reader["BalanceAmt"]);
BalanceBox.Text = myNum.ToString("C");
Note the "C" currency format specifier argument passed into the decimal.ToString method - see MSDN Decimal.ToString Method Documentation.
The Convert.ToDecimal method will throw an exception if reader["BalanceAmt"] contains anything that Convert.ToDecimal is unable to cope with (non-numeric characters).
You might want to put a try..catch around this, or if you don't want an exception to be thrown, use Decimal.TryParse inside an if check:
var balanceAmt = reader["BalanceAmt"];
if (decimal.TryParse(balanceAmt, out var myNum))
{
BalanceBox.Text = myNum.ToString("C");
}
while (reader.Read())
{
BalanceBox.Text = reader["BalanceAmt"].ToString("c");
}
In your code String.Format("{0:#,###0}", MyNum); MyNum never changes...only formatted.
Please use this:
BalanceBox.Text = String.Format("{0:#,###0}", Convert.ToDouble(MyNum));
Is there an easy way to check if a format string is valid? For example the following is code that we use to test a number format string;
public static bool IsValidFormatStringNumber(string FormatString)
{
try
{
const decimal number = 0.056m;
var formattedNumber = number.ToString(FormatString);
return formattedNumber.Length > 0;
}
catch
{
return false;
}
}
We're trying to catch an exception or determine if the resulting string has no length. This test fails however as a format string of "hsibbur" (Any rubbish) results in a string of "hsaibbur", which has length.
We want to do the same test for Percent and Date format string.
If you just want to check for standard format strings, just check that your format strings are part of that list.
If you want to check for custom format strings (that are not "Other" or "Literal strings"), you can probably craft a regex to do it.
Other than that, since format strings can be arbitrary strings, I don't think validation even applies.
If FormatString is equal to formattedNumber, that could be another case for returning false.
I'm trying to convert this string to double
Convert.ToDouble("1.12");
and this is the output
System.FormatException was unhandled.
Should I do something like this?
public static double ConvertToDouble(string ParseVersion)
{
double NewestVersion;
try
{
NewestVersion = Convert.ToDouble(ParseVersion);
}
catch
{
ParseVersion = ParseVersion.Replace('.', ',');
NewestVersion = Convert.ToDouble(ParseVersion);
}
return NewestVersion;
}
ConvertToDouble("1.12");
Or is there an easier solution?
double.Parse will use the current culture by default. It sounds like you want the invariant culture:
double d = double.Parse("1.12", CultureInfo.InvariantCulture);
EDIT: Just to be clear, obviously you shouldn't use this if you're trying to parse text entered by a user in a different culture. This is for use when you've received data in the invariant culture (as most machine-to-machine data text-based formats are) and want to enforce that when parsing.
You don't have to replace . to ,.. however a better way is to use the .net TryParse method like:
double d;
if (double.TryParse("your string data", out d)
{
Console.WriteLine(d);
}
Edit: Also note that by replacing . by , you are getting a wrong results, for instance 1.12:
double d = double.Parse(1.12);//d will equals to 1.12
double d = double.Parse(1,12);//d will equals to 112.0
Convert.ToDouble uses Double.Parse internally. If you are unsure of the culture context, you should use an overload of Double.Parse precising the culture:
double d = double.Parse("1.12", CultureInfo.InvariantCulture);
Keep in mind, this problem can depend on where the input string comes from. If it is read from a database as an object, you might solve your problem by keeping it as an object and using Convert.ToDouble() as follows:
public double Double_fromObject(object obj)
{
double dNum = 0.0;
if (obj.ToString() != string.Empty) // the Convert fails when ""
{
try
{
dNum = Convert.ToDouble(obj);
}
catch (SystemException sex)
{
// this class's error string
LastError = sex.Message;
}
}
return (dNum);
}
I would like to convert a string to double (very basic question isn't it ?)
string input = "45.00000";
double numberd = Double.Parse(input, CultureInfo.InvariantCulture);
=> my code works and I am very happy.
However I may have the following
string input = "";
double numberd = Double.Parse(input, CultureInfo.InvariantCulture);
In this case my code does not work and I get a Exception error ;(
I wonder how I can manage such situation. Ideally when I get this I would like to have my variable numberd equal to null.
Can anyone help me ?
Thx
Microsoft recommends using the Tester-Doer pattern as follows:
string input = "";
double numberd;
if( Double.TryParse(input, out numberd) )
{
// number parsed!
}
Use a Double for parsing, but a Double? for storing the value, perhaps?
Double number;
string input = ""; // just for demo purpose, naturally ;o)
Double? nullableNumber =
Double.TryParse(input, NumberStyles.Any, CultureInfo.InvariantCulture, out number)
? (Double?)number
: null;
// use nullableNumber
Primitive types like double cannot be null. You can have a nullable version with double? but, Double.Parse does not return a double? (just a plain double).
You could use Double.TryParse and check the return condition and set a double? to null accordingly if that would suit better.
Why not just catch the exception and set your variable?
double numberd;
try {
numberd = Double.Parse(input, CultureInfo.InvariantCulture);
} catch (System.FormatException e)
numberd = 0.0;
}
Alternatively, you can use Double.TryParse
Add an if statement comparing strings or surround with try/catch block.
Assuming you aren't worried about other invalid values besides empty strings, here's a simple one-liner:
Double? numberd = (input.Length == 0) ? null : (Double?)Double.Parse(input, CultureInfo.InvariantCulture);
mzabsky was on the right path, however his solution won't build and you shouldn't hard-code empty string - it's better to check the length of a string.
How about
Double? numberd = String.IsNullOrEmpty(str) ? null : Double.Parse(str)
In my application, I am parsing CSV files and I want these empty strings to be zero so I return 0.0 instead of null and it's all good.
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