Question

I’m trying to use a .NET Regex to validate the input format of a string. The string can be of the format

single digit 0-9 followed by
single letter A-Z OR 07 OR 03 or AA followed by
two letters A-Z

So 0AAA, 107ZF, 503GH, 0AAAA are all valid. The string with which I construct my Regex is as follows:

    "([0-9]{1})" +
    "((03$)|(07$)|(AA$)|[A-Z]{1})" +
    "([A-Z]{2})"

Yet this does not validate strings in which the second term is one of 03, 07 or AA. Whilst debugging, I removed the third term from the string used to construct the regex, and found that input strings of the form 103, 507, 6AA WOULD validate…….

Any ideas why, when I then put the third term back into the Regex, the input strings such as 1AAGM do not match?

Thanks
Tom

Answer 1

This is because your expression requires the strings with 03, 07 and AA to end right there ($ matches the end of input). Remove the $ from these sub-expressions, and move it to the end of the expression.

"^[0-9](03|07|AA|[A-Z])[A-Z]{2}$"