Proper way to test if a value is numeric in C#

I just need to know if the value is numeric. I don't need to do anything with the value. Is this the best way? Feel dirty creating a variable that I won't开发者_JAVA技巧 ever use beyond this:

int val;
if(int.TryParse(txtFoo.Text, out val))
{
    ....
}

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Yes, using the relevant TryParse method and ignoring the out parameter is the best way of doing this.

You may want to wrap this up into your own set of helper methods (which could specify the appropriate culture etc, if the default isn't right for you) and just return a bool without the out parameter to make them easier to call.

Of course, you need to work out what kind of parsing is most appropriate - even for integers, you need to consider whether the range of Int32 is enough for your use case. In my experience, most numeric input has its own "natural" range of valid values, which is unlikely to be exactly the range of any predefined type. You may therefore want to expand your helper methods to include the range of valid values to accept.

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"is numeric" is an ambiguous term.

• Culture-aware?
• Allow thousands and/or decimal separators?
• Allow scientific notation?
• Allow a sign (before? after?...)
• What range of values do you allow? Signed 32-bit integer (Int32.TryParse), Unsigned 32-bit integer (UInt32.TryParse), decimal, double, ...

Hence there is no "best" way, and the Framework provides a multitude of different ways to parse numbers.

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You can use Regular expressions

Regex _isNumber = new Regex(@"^\d+$");
_isNumber.IsMatch(txtFoo.Text);

This will only match Ints, but you can write one that also matches decimals.

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It's not as flexible as int.TryParse, but you could check to see if each character is a number:

bool isInt = txtFoo.Text.All(c => char.IsNumber(c));

In general, though, I would recommend sticking with int.TryParse. You can even call the unused parameter "ignored" to be explicit about your intent, e.g.:

int ignored;
bool isInt = int.TryParse(txtFoo.Text, out ignored);

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That is the recommended way of doing it in C#. However, you could also add Microsoft.VisualBasic.dll as a reference to your project and then use Microsoft.VisualBasic.Information.IsNumeric()

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You can try using Regex parsing to determine that there are no non-numeric characters in a string, or you can use Int.TryParse(), Double.TryParse(), Float.TryParse() depending on the input.

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bool test (string teststring) 
 { for (i=0;i==teststring.length;i++){
   if instr("0123456789.,-+Ee",teststring.substring(i,1) <0){return false;}
   // some additional tests below here if you like
   return true;
 }

however E1001E12e.12e would be noted as a number a little bit more magic is needed to do a clean check, but then you might be able to determine if its a int or a float too..

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That's the best way of doing it in my knowledge - that's what our company standards adhere to anyway due to the error handling being done within the parsing.

This details the advantages: https://web.archive.org/web/20150510214425/http://www.dotnetperls.com:80/int-tryparse