How to check if IsNumeric

Question

Possible Duplicate    How to identify if string contain a number        In VB there s an IsNumeric function  is there something similar in c      To get around it  I just wrote the code       if  Int32 Parse txtMyText Text Trim     gt  0    I was just wondering if there is a better way to do this

User · Answer

I think you need something a bit more generic. Try this:

public static System.Boolean IsNumeric (System.Object Expression)
{
    if(Expression == null || Expression is DateTime)
        return false;

    if(Expression is Int16 || Expression is Int32 || Expression is Int64 || Expression is Decimal || Expression is Single || Expression is Double || Expression is Boolean)
        return true;

    try 
    {
        if(Expression is string)
            Double.Parse(Expression as string);
        else
            Double.Parse(Expression.ToString());
            return true;
        } catch {} // just dismiss errors but return false
        return false;
    }
}

Hope it helps!

User · Answer

Other answers have suggested using TryParse  which might fit your needs  but the safest way to provide the functionality of the IsNumeric function is to reference the VB library and use the IsNumeric function   IsNumeric is more flexible than TryParse   For example  IsNumeric returns true for the string   100   while the TryParse methods all return false   To use IsNumeric in C   add a reference to Microsoft VisualBasic dll   The function is a static method of the Microsoft VisualBasic Information class  so assuming you have using Microsoft VisualBasic   you can do this   if  Information IsNumeric txtMyText Text Trim

User · Answer

You could write an extension method   public static class Extension       public static bool IsNumeric this string s                float output          return float TryParse s  out output

User · Answer

You should use TryParse method which Converts the string representation of a number to its 32-bit signed integer equivalent  A return value indicates whether the conversion succeeded       int intParsed      if int TryParse txtMyText Text Trim   out intParsed                    perform your code

User · Answer

There s the TryParse method  which returns a bool indicating if the conversion was successful

User · Answer

You should use TryParse - Parse throws an exception if the string is not a valid number - e g  if you want to test for a valid integer   int v  if  Int32 TryParse textMyText Text Trim    out v                 If you want to test for a valid floating-point number   double v  if  Double TryParse textMyText Text Trim    out v                 Note also that Double TryParse has an overloaded version with extra parameters specifying various rules and options controlling the parsing process - e g  localization      or      - see http   msdn microsoft com en-us library 3s27fasw aspx

User · Answer

There s a slightly better way   int valueParsed  if Int32 TryParse txtMyText Text Trim    out valueParsed             If you try to parse the text and it can t be parsed  the Int32 Parse method will raise an exception   I think it is better for you to use the TryParse method which will capture the exception and let you know as a boolean if any exception was encountered   There are lot of complications in parsing text which Int32 Parse takes into account   It is foolish to duplicate the effort   As such  this is very likely the approach taken by VB s IsNumeric   You can also customize the parsing rules through the NumberStyles enumeration to allow hex  decimal  currency  and a few other styles   Another common approach for non-web based applications is to restrict the input of the text box to only accept characters which would be parseable into an integer   EDIT   You can accept a larger variety of input formats  such as money values    100   and exponents   1E4    by specifying the specific NumberStyles   int valueParsed  if Int32 TryParse txtMyText Text Trim    NumberStyles AllowCurrencySymbol   NumberStyles AllowExponent  CultureInfo CurrentCulture  out valueParsed                 or by allowing any kind of supported formatting   int valueParsed  if Int32 TryParse txtMyText Text Trim    NumberStyles Any  CultureInfo CurrentCulture  out valueParsed

[c#] How to check if IsNumeric

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