Question

Guys I hate Regex and I suck at writing.

I have a string that is space separated and contains several codes that I need to pull out. Each code is marked by beginning with a capital letter and ending with a number. The code is only two digits.

I’m trying to create an array of strings from the initial string and I can’t get the regular expression right.

Here is what I have

String[] test = Regex.Split(originalText, "([a-zA-Z0-9]{2})");

I also tried:

String[] test = Regex.Split(originalText, "([A-Z]{1}[0-9]{1})");

I don’t have any experience with Regex as I try to avoid writing them whenever possible.

Anyone have any suggestions?

Example input:

AA2410 F7 A4 Y7 B7 A 0715 0836 E0.M80

I need to pull out F7, A4, B7. E0 should be ignored.

Answer 1

You want to collect the results, not split on them, right?

Regex regexObj = new Regex(@"\b[A-Z][0-9]\b");
allMatchResults = regexObj.Matches(subjectString);

should do this. The \bs are word boundaries, making sure that only entire strings (like A1) are extracted, not substrings (like the A1 in TWA101).

If you also need to exclude “words” with non-word characters in them (like E0.M80 in your comment), you need to define your own word boundary, for example:

Regex regexObj = new Regex(@"(?<=^|\s)[A-Z][0-9](?=\s|$)");

Now A1 only matches when surrounded by whitespace (or start/end-of-string positions).

Explanation:

(?<=  # Assert that we can match the following before the current position:
 ^    # Start of string
|     # or
 \s   # whitespace.
) 
[A-Z] # Match an uppercase ASCII letter
[0-9] # Match an ASCII digit
(?=   # Assert that we can match the following after the current position:
 \s   # Whitespace
|     # or
 $    # end of string.
)

If you also need to find non-ASCII letters/digits, you can use

\p{Lu}\p{N}

instead of [A-Z][0-9]. This finds all uppercase Unicode letters and Unicode digits (like Ä٣), but I guess that’s not really what you’re after, is it?