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 am working on a Page where I have several Entries to enter numerical values (integers and with decimal point).
The requirement is that each field formats the value with decimal point and thousands separators (eg: 1.254.356,42).
The following code formats the value correctly. The problem is that the cursor does jumps to the end always when the text changes:
private void TbLenght_TextChanged(object sender, TextChangedEventArgs e)
{
var textbox = (Entry)sender;
var tempValue = double.Parse(textbox.Text, culture);
var newFormat = tempValue.ToString("N2", culture);
textbox.Text = newFormat;
}
Which options do I have to achieve my goal?
The following code formats the value correctly. The problem is that the cursor does jumps to the end always when the text changes:
You can change current CursorPosition for entry to make current CursorPosition before the decimal point, please take a look the following code:
var textbox = (Entry)sender;
var tempValue = double.Parse(textbox.Text, culture);
var newFormat = tempValue.ToString("N2", culture);
textbox.Text = newFormat;
textbox.CursorPosition = newFormat.Length-3;
If my reply solved your issue, please remember to mark my reply as answer, thanks.
I am trying to get myself used to C#, currently I am using SharpDevelop for that Task, anyway, I have a simple question, let's say I want to have a TextBox that Shows me the outcome of a mathematical code as shown below, how do I get the TextBox to actually Show me types like double, int, or other stuff? It always tells me it can't convert double to string or whatever, I am pretty noob so yeah.
void CmdWriteClick(object sender, EventArgs e)
{
double var = 8.40;
double start = 9.00;
double end = var + start;
textbox_end.Text = end;
}
I already tried to not use the .text but something like. value but didn't work, any help?
Just add .ToString()
textbox_end.Text = end.ToString()
You can try wrapping it in a string, like:
void CmdWriteClick(object sender, EventArgs e)
{
double var = 8.40;
double start = 9.00;
double end = var + start;
textbox_end.Text = "" + end + "";
}
private void TextBox_TextChanged(object sender, EventArgs e)
{
string value = TextBox.Text.Replace(",", "");
double dbl;
if (double.TryParse(value, out dbl))
{
TextBox.TextChanged -= TextBoxTextChanged;
TextBox.Text = string.Format("{0:#,#0}", dbl);
TextBox.SelectionStart = TextBox.Text.Length;
TextBox.TextChanged += TextBoxTextChanged;
}
}
I used above code for making Calculator. I want to get results comma with decimal value. I want to type 1,234.1234 in the
textBox, but I can not type 1,234.1234 in the Text Box. I mean comma with decimal value not getting.
Can anybody kindly please help me to solve this problem ?
You have to provide a Culture that uses . as thousands sign.
Normally you want to use the users current culture.
double.TryParse(value, System.Globalization.NumberStyles.Number, System.Globalization.CultureInfo.CurrentCulture, out dbl)
Try this:
int value = 300000
String.Format("{0:#,###0}", value);
// will return 300,000
http://msdn.microsoft.com/en-us/library/system.string.format.aspx
I'm using WinForm. I have 2 textboxes.
Goal: I want textBox1 to mirror the numbers I type in textBox2
Problem: All numbers work, except when I type in 0 in the beginning.
Test Case:
textBox1 = 1203 - correct works
textBox2 = 1203 - correct works
textBox1 = 0123 - works
textBox2 = 123 - Does not match textBox1
private void textBox1_TextChanged(object sender, EventArgs e)
{
try
{
int numb1, result;
numb1 = Convert.ToInt32(textBox1.Text);
result = numb1;
textBox2.Text = result.ToString();
}
catch (Exception)
{
textBox2.Text = "";
}
}
That's expected due the conversion of your Text string to a number. A leading zero is meaningless in a number and when you convert that number back to a string there will be no leading zero. So, just copy the Text property without conversion.
However, if this code is a tentative to validate the input then use Int32.TryParse instead of Convert.ToInt32
private void textBox1_TextChanged(object sender, EventArgs e)
{
int numb1;
if(Int32.TryParse(textBox1.Text, out numb1))
textBox2.Text = textBox1.Text;
else
{
MessageBox.Show("Invalid number");
textBox2.Text = "";
}
}
Int32.TryParse remove the necessity to use a try/catch because if the conversion fails it just return false. Instead Convert.ToInt32 raises an exception. In general terms, if you have the possibility to avoid an exception, then use that possibility instead of drive your logic catching excetions
try this:
textBox1.Text = int.Parse(textBox2.Text) == 0 ? "0" : textBox2.Text;