Question

I have the regex: (?ms)(?<attribute>\[.+?\]|public|private|\s)+?class

and I have the text:

[attribute]
public int a;

[attribute C]
[attribute B]
public class Test{

}

I would like to know why the regex that I posted matches:

[attribute]
public int a;

[attribute C]
[attribute B]
public class

I think it should match:

[attribute C]
[attribute B]
public class

---

Correct me if I am wrong. I think the way that the regex is supposed to be read is:

Find either an attribute ( [ some attribute ] ) or public key word or private keyword or space.

So first the regex engine should match [attribute], then the ‘\n’ (new line), then the public keyword. After these, the keyword int is not an option, so why does it match it?

Answer 1

The problem is that you are using a dot which matches anything, including close square brackets, whitespace, and (in single-line mode) newlines:

\[.+?\]

You should use this instead:

\[[^\]]+\]

Explanation:

\[     Match a literal open square bracket.
[^\]]  Match any character except a close square bracket.
+      One or more.
\]     Match a literal close square bracket.