Regexp for string stating with a + and having numbers only

Question

I have the following regex for a string which starts by a + and having numbers only:

PatternArticleNumber = $"^(\\+)[0-9]*";

However this allows strings like :

+454545454+4545454

This should not be allowed. Only the 1st character should be a +, others numbers only. Any idea what may be wrong with my regex?

Answer 1

You can probably workaround this problem by just adding an ending anchor to your regex, i.e. use this:

PatternArticleNumber = $"^(\\+)[0-9]*$";

Demo

The problem with your current pattern is that the ending is open. So, the string +454545454+4545454 might appear to be a match. In fact, that entire string is not a match, but the engine might match the first portion, before the second +, and report a match.