Need help with Regular Expression for nine digit alphanumeric with minimum one space boundary

I'm trying to match a CUSIP number. I have the following, but it is missing some edge cases.

\s[A-Za-z0-9]{9}\s

I need to omit strings which contain a space in the middle and I need it to match strings which may be bordered by some other text. My strings are generally surrounded by tabs, but it开发者_如何转开发 may be as little as one space char separating the CUSIP from other text. Thanks in advance, I'm pretty green with regex. P.S. I'm working in .NET

Example

"[TAB]123456789[TAB]" should be matched (I'm getting this now)

"sometext[TAB]123456789[TAB]sometext" should be matched (this is not currently being returned)

"some text" should not be returned (I am currently getting this kind of match)

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The other answers are wrong, not taking into account PPNs and allowing the check digit to be a letter. Therefore, here's a better solution.

Based on this document and this document, the CUSIPs have the following rules:

• Length is 9 characters.
• Characters 1, 2, 3 are digits.
• Characters 4, 5, 6, 7, 8 are either letters or digits.
• Characters 6, 7, 8 can also be *, @, #.
• Character 9 is a check digit.

With this in mind, the following regex should provide a tight match:

^[0-9]{3}[a-zA-Z0-9]{2}[a-zA-Z0-9*@#]{3}[0-9]$

You can play around with it here.

Note that this is as tight as possible without diving into too much details, which would turn the expression into a monster. I suggest you use the check digit algorithm to fully validate the CUSIP, which you can find here.

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According to this page, not just any 9-digit alphanumeric is a valid CUSIP. The first three characters can only be digits, and the ninth is a checksum So if you want to distinguish CUSIPs from other 9-character strings, I believe this should work better:

\s[0-9]{3}[a-zA-Z0-9]{6}\s

or, if you also want to match strings that are bordered by the beginning or end of input:

(^|\s)[0-9]{3}[a-zA-Z0-9]{6}(\s|$)

or, if you also want to match strings that are bordered by punctuation (such as "(100ABCDEF)":

(^|[^a-zA-Z0-9])[0-9]{3}[a-zA-Z0-9]{6}([^a-zA-Z0-9]|$)

I believe that should be a 99% solution, but if you want to be really robust you might also want to look into using the 9th (parity) character to verify that the strings are valid.

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string haystack = "some 123456789 text";//single space separators

string haystack2 = "some\t123456789\ttext";//tab separators

// The comment is correct, your pattern was correct originally.  
// This is just slightly dressed up.
string pattern = @"(\s+)(?<cusip>[A-Za-z0-9]{9})(\s+)";

Match m = Regex.Match(haystack, pattern);

Console.WriteLine("Match for cusip surrounded by spaces:" + m.Groups["cusip"]);
//Output: Match for cusip surrounded by spaces:123456789

Match m2 = Regex.Match(haystack2, pattern);

Console.WriteLine("Match for cusip surrounded by tabs:" + m2.Groups["cusip"]);
//Output: Match for cusip surrounded by tabs:123456789

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    public Boolean CusipValidation(string sCusip)
    {
        string Cusippattern = @"^([0-9]){3}([a-zA-Z0-9]){6}$";

        if (!System.Text.RegularExpressions.Regex.IsMatch(sCusip, Cusippattern, System.Text.RegularExpressions.RegexOptions.IgnoreCase) && sCusip != string.Empty)
            return false;
        else
            return true;
    }