RegExp multiply matches in text

Question

I want to write a regexp to get multiple matches of the first character and next three digits. Some valid examples: A123, V322, R333. I try something like that

[a-aA-Z](1)\d3

but it gets me just the first match! Could you possibly show me, how to rewrite this regexp to get multiple results?Thank you so much and Have a nice day!

Answer 1

Your regex does not work because it matches:

• [a-aA-Z] - an ASCII letter, then
• (1) - a 1 digit (and puts into a capture)
• \d - any 1 digit
• 3 - a 3 digit.

So, it matches Y193, E103, etc., even in longer phrases, where Y and E are not first letters.

You need to use a word boundary and fix your pattern as

\b[a-aA-Z][0-9]{3}

NOTE: if you need to match it as a whole word, add \b at the end: \b[a-aA-Z][0-9]{3}\b.

See the regex demo.

Details:

• \b - leading word boundary
• [a-aA-Z] - an ASCII letter
• [0-9]{3} - 3 digits.

C# code:

var results = Regex.Matches(s, @"\b[a-aA-Z][0-9]{3}")
        .Cast<Match>()
        .Select(m => m.Value)
        .ToList();