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re: IsNumeric in C#, WHY NOT?

Praveen — Mon, 18 Aug 2008 06:34:23 GMT

In .Net 2005 the best form of IsNumeric is as follows.

public static bool IsNumeric(string argument)

{

float result ;

return float.TryParse(argument,out result);

}

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re: IsNumeric in C#, WHY NOT?

Wilby Jackson — Wed, 06 Aug 2008 16:28:49 GMT

Revised to actually check for a number either int or decimal.

public static bool isNumeric(string str)

{

//number of decimals in string

int decCounter = 0;

//loop through checking each char for a number or dec.

foreach (char c in str)

{

if (!char.IsNumber(c) && !c.Equals('.'))

{

return false;

}

else if (c.Equals('.') && decCounter >= 1)

{

return false;

}

else if (c.Equals('.'))

{

decCounter += 1;

}

//before returning true make sure there is not a decimal at the end of the string

if (!(decCounter > 1))

{

return true;

}

else

{

return false;

}

re: IsNumeric in C#, WHY NOT?

Deon van Staden — Thu, 31 Jul 2008 23:14:40 GMT

Looking at this old blog, I decided to add something else. I found this very nice link and thought I should share it.

sadeveloper.net/.../8887.aspx

The part I really agree with it w.r.t. RegEx.

Here is a snippet from the post:

// Define a regular expression for currency values.

Regex rx = new Regex(@"^-?\d+(\.\d{2})?$");

// Define some test strings.

string[] tests = {"-42", "19.99", "0.001", "100 USD"};

// Check each test string against the regular expression.

foreach (string test in tests)

{

if (rx.IsMatch(test))

{

Console.WriteLine("{0} is a currency value.", test);

}

else

{

Console.WriteLine("{0} is not a currency value.", test);

}

And then this part also enhances this a lot:

To add negative validation to the beginning, start the regular expression with an optional hyphen.

Immediately after the "start of text" marker (which looks like "^") put in a hyphen and a question mark. The question mark allows zero or one of the preceding character (a hyphen) but no more.

^-?\d+$ (this is for negative and positive integers)

^-?\d+([\.]{1}\d*)?$ (this is for negative and positive decimals)

Spread the word about Regular Expressions. I love them. They become much easier if you use a tool like "Expresso". I have created a regular expression that I use to validate password complexity in javascript on the client browser (more than 6 chars, includes number or capitals or special characters in various combinations - its one long string or about five readable lines when broken apart).

Thanks jamesh. I think this one wins the competition thus far. I would like to see what Microsoft is going to come up with when they wake up with IsNumeric?

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re: IsNumeric in C#, WHY NOT?

zamkinos — Wed, 16 Jul 2008 08:08:49 GMT

thanks a lot.

re: IsNumeric in C#, WHY NOT?

James McConville — Thu, 19 Jun 2008 11:36:05 GMT

I Like this method... (apologies if its already on the coversation, i didn't read all the posts)

...

int output;

if (int.TryParse("123", out output))

{

return true;

}

else

{

return false;

}

re: IsNumeric in C#, WHY NOT?

Wilby Jackson — Tue, 03 Jun 2008 18:59:19 GMT

This also works as a replacement:

public bool isNumeric(string str)

{

bool isNumber = false;

foreach (char c in str)

{

if (char.IsNumber(c))

{

isNumber = true;

}

return isNumber;

}

re: IsNumeric in C#, WHY NOT?

Ken Palmer — Wed, 28 May 2008 13:15:09 GMT

TryParse() is a viable alternative to Try/Catch. When a conversion fails it returns False rather than an exception.

The code I'm using below was adapted from Microsoft and Scott Hanselman's blog:

support.microsoft.com/.../329488

www.hanselman.com/.../ExploringIsNumericForC.aspx

public static bool IsNumeric(object expression)

{

if (expression == null) { return false; }

double retNum; // Collects out parameter of TryParse(). If conversion fails the out parameter is zero.

// TryParse() returns True when conversion passes and False when conversion fails. It doesn't generate an exception.

return Double.TryParse(Convert.ToString(expression), System.Globalization.NumberStyles.Any, System.Globalization.NumberFormatInfo.InvariantInfo, out retNum);

}

re: IsNumeric in C#, WHY NOT?

senthilkumar — Fri, 25 Apr 2008 06:00:10 GMT

protected bool CheckforNumber(string strNumber)

{

try

{

Int64 no1 = Convert.ToInt64(strNumber);

return true;

}

catch (FormatException FE)

{

return false;

}

re: IsNumeric in C#, WHY NOT?

senthil — Fri, 25 Apr 2008 05:57:25 GMT

protected bool CheckforNumber()

{

string no = "";

try

{

Int64 no1 = Convert.ToInt64(no);

return true;

}

catch (FormatException FE)

{

return false;

}

re: IsNumeric in C#, WHY NOT?

Dave — Thu, 20 Mar 2008 20:58:53 GMT

Using the VB namespace is the best way to go. Just look at how many code samples were presented with errors.

re: IsNumeric in C#, WHY NOT?

sambo — Tue, 18 Mar 2008 13:32:09 GMT

private bool IsNumeric(string inputString)

{

return Regex.IsMatch(inputString, "^[0-9]+$");

}

Good practice and performance, my think.

re: IsNumeric in C#, WHY NOT?

Txomin — Mon, 28 Jan 2008 10:37:30 GMT

This one matches thousand separators

private bool isNumeric(string stringToCheck)

{

System.Text.RegularExpressions.Regex _isNumber =

new System.Text.RegularExpressions.Regex

(@"(^[-+]?\d+(,?\d*)*\.?\d*([Ee][-+]\d*)?$)|(^[-+]?\d?(,?\d*)*\.\d+([Ee][-+]\d*)?$)");

return _isNumber.Match(stringToCheck).Success;

}

re: IsNumeric in C#, WHY NOT?

Chris Tagg — Thu, 25 Oct 2007 14:45:38 GMT

Any ideas for an IsDate()?