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Regex real number

I need real numbers in TextBox. I try my code online here
"^-{0,1}[0-9]{1,3},{0,1}[0-9]{1,2}$"
and its working perfectly, but in my project not working.
Please show me how I must do it

Would TryParse works for you? From MSDN:
Converts the string representation of a number in a specified style and culture-specific format to its double-precision floating-point number equivalent. A return value indicates whether the conversion succeeded or failed.
And for you, it could be something like this:
private void c_PreviewTextInput(object sender, TextCompositionEventArgs e)
{
double num;
e.Handled = double.TryParse(e.Text, out num);
// if e.Text is a number, e.Handled will be true and num = e.Text
}

Calculator - thousand separator by comma in c#

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

How to use Regex to only allow a certain length for individual values in a comma-separated list?

I have a TextBox where I want to let users enter hexadecimal values (excluding the 0x prefix) in a comma separated list. The problem is that I only want each value to be a length of four characters. Following this answer, I use the KeyPress event handler to do this check that the user can only enter a digit:
private void filterIDTextBox_KeyPress(object sender, KeyPressEventArgs e)
{
if (!Char.IsControl(e.KeyChar) && !Char.IsDigit(e.KeyChar))
{
e.Handled = true;
}
}
With Regex, we can restrict the user even more to only allow 0-9, A-F, a-f, and comma like this:
private void filterIDTextBox_KeyPress(object sender, KeyPressEventArgs e)
{
if (!Char.IsControl(e.KeyChar) && !Regex.IsMatch(e.KeyChar.ToString(), "[0-9A-Fa-f,]"))
{
e.Handled = true;
}
}
Is there any way I can use regex to make sure there are no more than 4 characters in between each comma? I tried using "[0-9A-Fa-f,]{0:4}" but this didn't work because I am doing the match only on the char, not the TextBox's text.
With that, I'm sure I'll have to use something other than KeyPress, but I still have been unsuccessful in writing the Regex statement for only allowing values up to 4 characters.

First you need to validate the entire text for this to work so validate filterIDTextBox.Text plus the key that was pressed. Second you need a regular expression that validates the entire field.
private void filterIDTextBox_KeyPress(object sender, KeyPressEventArgs e)
{
string newValueIfAllowed = filterIDTextBox.Text + e.KeyChar.ToString();
if (!Char.IsControl(e.KeyChar)
&& (!Regex.IsMatch(e.KeyChar.ToString(), "[0-9A-Fa-f,]")
|| !Regex.IsMatch(newValueIfAllowed , "^([0-9A-Fa-f]{1,4},)*[0-9A-Fa-f]{0,4}$")))
{
e.Handled = true;
}
}
That will allow any number of 1 to 4 digit hex values followed by a comma then followed by 0 to 4 more hex digits. That means that 123,456, is valid, but you need that to be valid to allow the user to type in the comma and continue.
An alternative is to wait and validate after the user enters a value and presses some type of submit button. Then you could change the expression to not allow blank values or trailing commas by changing the {0,4} to {1,4}.
Note: this assumes the user only types characters at the end of the text box if they move the cursor around you'll have to take that into account. Also selecting text and replacing it and copy-and-paste actions would also be problematic.

Bool test on a string gives unexpected result

This should be self explanatory. I am trying to detect if the first char of the string foo is a negative sign '-'. This is just a test code to test it.
private void button1_Click(object sender, EventArgs e)
{
string foo = textBox1.Text;
bool negativeValue = foo[1]==('-');
//bool negativeValue = foo[1].Equals ('-');
if (negativeValue == true)
{
label1.Text = "First char is negative !";
}
else if (negativeValue == false)
{
label1.Text = "First char is not negative !";
}
}
The result is always false even if the first char in the text box is '-'. Why?

Index lookup in C# is zero-based. So you should call:
foo[0] == ('-')
Using 1 will lookup the second character.
EDIT: Also as an alternative (and perhaps more clear) you can always use:
foo.StartsWith("-")
That should work no matter how inebriated you are. :)
(Also, consider trimming the text input if you want to avoid excessive/accidental preceding spaces from user input)

You are using wrong index.With 1 you are actually referring to 2nd character
Use 0
bool negativeValue = foo[0]==('-');

TextBox Validation - C#

I am having quite a hard time with my C# Application's textbox validation. The thing is, the said textbox should only accept decimal values. so it means, there should be no letters or any other symbols aside from the '.' symbol. The letter filter, i can handle. However, i don't exactly know how I can manage to filter the number of '.' that the textbox should accept. If anybody has any idea how to do this, please give me an idea.
Thank you very much :)

decimal value;
bool isValid = decimal.TryParse(textBox.Text, out value);
if (!isValid)
{
throw new ArgumentException("Input must be a decimal value");
}

this should work!!!
modified for just one decimal
private void txtType_KeyPress(object sender, KeyPressEventArgs e)
{
if (e.KeyChar == (char)Keys.Back || (e.KeyChar == (char)'.') && !(sender as TextBox).Text.Contains("."))
{
return;
}
decimal isNumber = 0;
e.Handled = !decimal.TryParse(e.KeyChar.ToString(), out isNumber);
}

Use regex validation:
^([0-9]*|\d*\.\d{1}?\d*)$
This site has a library of regex validation (including numeric related) that you'll find useful:
http://regexlib.com/Search.aspx?k=decimal&c=-1&m=-1&ps=20

Just a thought: if you are monitoring the decimal places, simply keep a bool flag in your control to say "I've already had a dot"; subsequent dots are invalid.
Alternatively, when checking for decimal places, you can use Contains:
if (textbox.Text.Contains("."))
Also, review this sample available on MSDN (NumericTextBox):
http://msdn.microsoft.com/en-us/library/ms229644(VS.80).aspx

Use a MaskedTextBox instead and set the mask to only accept decimals.