This is quite a popular request! It seems you might be disappointed, though - C# whidbey doesn't have it.
Instead you can do a

int.TryParse(string s, out int result)

which is quite nice, as you get the result back if the parse can be done successfully ;)

Deon, I am using exactly the same one you have there :)

I believe this was discussed (among other things) with Anders Hejl......berg during a whiteboard session at TechEd (USA). Apparently, a video of that session will be up on MSDNTV at some point.

we had a discussion on the forum at sadeveleoper about htis very topic ...

http://www.sadeveloper.net/Forum/ShowPost.aspx?PostID=9668

Good Job Guys.

Because numbers are for idiots ;-)

This might be a little bit faster

internal static bool IsNumeric(string numberString)
{
foreach (char c in numberString)
{
if (!char.IsNumber(c))
return false;
}
return true;
}

This method (as posted) just solved my problems. Yippeeee.

public static bool IsNumeric(object Expression)
{
bool isNum;
double retNum;
isNum = Double.TryParse(Convert.ToString(Expression), System.Globalization.NumberStyles.Any,System.Globalization.NumberFormatInfo.InvariantInfo, out retNum );
return isNum;
}

Try this ...
static bool IsNumeric(string input)
{
bool flag = true;

//Valid user input
string pattern = @"^[0-9]*$";
Regex validate = new Regex(pattern);

//Check the user input format
if(!validate.IsMatch(input))
{
flag = false;
}

return flag;
}

Even easier:

static bool IsNumeric(string inputString)
{
return Regex.IsMatch(inputString, "^[0-9]+$");
}

I posted an article about this as well (as it relates to performance):

http://jaysonknight.com/blog/articles/1756.aspx

I haven't taken the time to check all of these great examples out, but I did notice with the second example from the bottom (in the article) that the function did not return true or false if an empty string was submitted.
(this is for an asp.net page I am testing)

I added a simple if statement using string.Empty that would return false if the string was empty.

internal static bool IsNumeric(string numberString)
{


if (numberString==string.Empty) return false;

     char [] ca = numberString.ToCharArray();
     for (int i = 0; i < ca.Length;i++)
     {
           if (!char.IsNumber(ca))
           return false;
     }
     return true;
}

Another option ..

I'm not knowledgeable enough to know if there are perfomance issues associated with referencing a component.

(1)  Create a class in visual basic such as ..

Public Class VB

    Public Shared Function IsNumeric(ByVal s As String) As Boolean

         Return Microsoft.VisualBasic.IsNumeric(s)

    End Function

End Class

(2)  Reference your class in C# and use it like ...

   if( VB.IsNumeric("some string") ) {;}

Why create a class? Just reference the function directly from the Microsoft.VisualBasic library, i.e.

using Microsoft.VisualBasic;

...

if (Information.IsNumeric(myString)) ...

Brilliant - using VB functions in a C# program, why not!  I am going to try that one.

Many of the functions presented here forget that decimal points, commas, and minus signs are part of numeric fields also!  And those that try converting to integers forgot about decimal numbers I guess.

Here is my offering:

/// <summary>

/// IsANumber() - returns TRUE if the input string contains only number characters.

///                      Empty strings are considered non-numeric.

/// </summary>

/// <param name="text"></param>

/// <returns></returns>

private bool IsANumber(string text)

{

bool isnumber = false;

if (text.Length > 0)

{

char[] legalchars = "0123456789,.-".ToCharArray();

isnumber = true; // innocent until proven guilty

// look for the first non-numeric character in the input string

for (int i = 0; i < text.Length; i++)

{

// if the character is NOT in the list of valid characters, it is not a number

if (text.LastIndexOfAny(legalchars,i,1) < 0)

{

isnumber = false;

break;

}

}

}

return isnumber;

}

Hello

you can test this one.

public static bool IsNumeric(string theValue)

{

  Regex _isNumber = new Regex(@"^\d+$");

  Match m = _isNumber.Match(theValue);

  return m.Success;

}

You stupid stupid people...

---

using System.Text.RegularExpressions;

public bool IsNumeric(string str)

{

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

}

TO: Adaptable Objects

try to parse str = "01" with regex.

For all those VB fans (And I am one of them). The VB IsNumeric interally actually does a try catch so is no better than C#'s  Int32.Parse(s);

Thanks guys... This was quite helpful...

I guess I might need to bookmark this site, as I'm still a newbie in C# and I might need useful thoughts of other C# programmers...

Thanks Sir:

Very well,u doing very well job.Keep it up!

easy....

using System.Text.RegularExpressions;

           MessageBox.Show(Regex.IsMatch("Hi","^[0-9]").ToString());   //false

           MessageBox.Show(Regex.IsMatch("1", "^[0-9]").ToString());  //true

           MessageBox.Show(Regex.IsMatch("123", "^[0-9]").ToString());  //true

           MessageBox.Show(Regex.IsMatch("01", "^[0-9]").ToString());  //true

           MessageBox.Show(Regex.IsMatch("0", "^[0-9]").ToString());   //true

           MessageBox.Show(Regex.IsMatch("-1", "^[0-9]").ToString());   //false

by further tailoring the expression a tiny bit, you can allow or disallow leading zeros, negatives, decimals, etc...

just do a google on how to use Regex.

It's funny how there's not a single solution in the comments that will give the correct result for all of the following:

123..4 (Not a number)

12Hello (Not a number)

-12.34 (Number)

0123 (Number; octal, not decimal)

Here's a regular expression that only matches valid decimal numbers:

^-?(?:0|[1-9][0-9]*)(?:\.[0-9]+)?$

You would use it like so:

public static bool IsNumeric(string value) {

return Regex.IsMatch(value, @"^-?(?:0|[1-9][0-9]*)(?:\.[0-9]+)?$");

}

It was made for non-formatted numbers and will not match thousand separators (besides, some countries use space as separators and commas as the decimal point, etc.)

One could argue that it should also match decimal numbers with zero omitted (.123), but that would require a more complex regular expression (or if you make sure the string is not empty or equal to "-" and add a ? after the first group, that will work too).

It returns false for numbers like 0123 (this is a number, but an octal/base-8 one.)

What's even more funny is that the originally proposed solution is just as good (except it reads 0123 as decimal 123, but on the other hand it reads .123 as 0.123):

decimal result;

if (Decimal.TryParse(value, out result))

{

// It's a number and you now have its value in the result variable.

}

Any ideas for an IsDate()?

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;

}

private bool IsNumeric(string inputString)

{

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

}

Good practice and performance, my think.

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

protected bool CheckforNumber()

   {

       string no = "";

       try

       {

           Int64 no1 = Convert.ToInt64(no);

           return true;

       }

       catch (FormatException FE)

       {

           return false;

       }

   }

protected bool CheckforNumber(string strNumber)

   {  

       try

       {

           Int64 no1 = Convert.ToInt64(strNumber);

           return true;

       }

       catch (FormatException FE)

       {

           return false;

       }

   }

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);

}

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;

   }

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;

           }

thanks a lot.

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?

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;

          }

       }

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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);

}

Hi all,

i'm having problem in custom paging using web application..there is an error saying "Input string was not in a correct format."

Here is my coding..

protected void NavigationLink_Click ( Object sender, CommandEventArgs e )

{

switch ( e.CommandName )

{

case "First":

_currentPageNumber = 1;

break;

case "Last":

_currentPageNumber = Int32.Parse(TotalPages.Text);

break;

case "Next":

_currentPageNumber = Int32.Parse(CurrentPage.Text) + 1;

break;

case "Prev":

_currentPageNumber = Int32.Parse(CurrentPage.Text) - 1;

break;

}

BindData();

}

public void BindData()

{

OdbcConnection myconn;

myconn= new OdbcConnection ("DSN=myodbc2;SERVER=localhost;DATABASE=misdb;UID=root;PORT=3306");

OdbcCommand cmd2 = new OdbcCommand("Select * from registration", myconn);

cmd2.CommandType=CommandType.StoredProcedure;

cmd2.Parameters.Add(new OdbcParameter ("@CurrentPage",OdbcType.Numeric,10)).Value=_currentPageNumber;

cmd2.Parameters.Add(new OdbcParameter("@PageSize",OdbcType.Numeric,10)).Value=DataGrid.PageSize;

cmd2.Parameters.Add(new OdbcParameter("@TotalRecords",OdbcType.Numeric,10)).Direction =ParameterDirection.Output;

try

{

myconn.Open();

DataGrid.DataSource=cmd2.ExecuteReader();

DataGrid.DataBind();

}

finally

{

myconn.Close();

}

CurrentPage.Text=_currentPageNumber.ToString();

Double _totalPages = 1;

if ( !Page.IsPostBack )

{

Int32 _totalRecords = (Int32) cmd2.Parameters["@TotalRecords"].Value;

totalPages = _totalRecords / DataGrid.PageSize;

TotalPages.Text =(System.Math.Ceiling(_totalPages)).ToString();

}

else

{

_totalPages = Double.Parse(TotalPages.Text);

}

if ( _currentPageNumber == 1 )

{

PreviousPage.Enabled = false;

if ( _totalPages > 1 )

{

NextPage.Enabled = true;

}

else

{

NextPage.Enabled = false;

}

}

else

{

PreviousPage.Enabled = true;

if ( _currentPageNumber == _totalPages )

{

NextPage.Enabled = false;

}

else

{

NextPage.Enabled = true;

}

}

}

Pls help me..

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