CODEWITHSUNDEEP
c#.netregex
obratim
obratim

Reputation: 566

.NET regex match and replace

My task is to verify a string with regex, than perform replacement if it match succeed or throw Exception if string don't match.

Obviously, I could check Regex.IsMatch and then call Regex.Replace or throw Exception:

var str = "89991112233";
var pattern = @"(?<prefix>8|\+?\d+)\s*(?<code>\d{3,3})\s*(?<phone>\d{7,7})";
var replace = "+7 ${code} ${phone}";

if (!Regex.IsMatch(str, pattern))
    throw new Exception();
else
    return Regex.Replace(str, pattern, replace);

but it requires two identical matching operations.

Can I perform regex check and get both if string was matching and the replacement in single call in .Net?

Upvotes: 5

Views: 1718

Answers (1)

Wiktor Stribiżew
Wiktor Stribiżew

Reputation: 627607

You may set a flag and set it to true if there was a match and then check if the flag was set to decide whether to throw the exception or return the string:

var str = "89991112233";
var pattern = @"^(?<prefix>8|\+?\d+)\s*(?<code>\d{3})\s*(?<phone>\d{7})\z";
var matched = false;
var result = Regex.Replace(str, pattern, m => {
    matched = !matched;
    return $"+7 ({m.Groups["code"].Value}) {m.Groups["phone"].Value}";
});
if (!matched)
    throw new Exception();
else
    return result;

Also, note that to match a whole string with the regex, you need anchors, I added ^ at the start and \z at the end.

Also, {3,3} is equal to {3} and {7,7} to {7}.

Upvotes: 5

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