Regular expression:parse namespaces in c# source code

Question

I wanna parse namespaces in c# cs file, for example using System.Collections.Generic I want to capture groups (System) (Collections) (Generic).

So far i wrote this regular expression: "[ .]?(\w*?)(?=[.;])"

but it also marks every words which suits this pattern.

So I have to add condition that line begins with "using".

I tried to add this "using[ .]?(\w*?)(?=[.;])" but it will only capture first namespace.

There is input text

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.IO;
using System.Text.RegularExpressions;

string someString;
Console.ReadLine();

Update:

I'm sorry I didn't mentioned it first, but there is one more thing, the same thing will happen with Methods, for example, Console.ReadLine() shouldnt return ReadLine. The same for all dots that are not in using

What about using 2 regexes? One for getting everything after using, then another for getting the subnamespaces. — Sweeper
– Sweeper, Commented Mar 10, 2019 at 8:40

revo · Accepted Answer · 2019-03-10 09:47:07Z

2

To start to match repeating patterns from a specific point you will find \G token helpful:

(?m)(?:^using +|\G(?!^)\.)\K\w+

See live demo here

Regex breakdown:

(?m) Enable multiline mode
(?: Start of non-capturing group
- ^using + Match using at start of line following spaces
| Or
- \G(?!^) Start match from where previous match ended
- \. Match a period
) End of non-capturing group
\K Reset output
\w+ Match a sequence of word characters

answered Mar 10, 2019 at 9:47

revo

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3 Comments

Allan Over a year ago

Super nice answer, I didn't know \G and \K. So powerful, I will I could vote more than one time. By the way, wouldn't (?m)(?:^using +|\G\.)\K\w+ work fine as well?

revo Over a year ago

Thank you. No, omitting lookahead will cause engine to match .someString at the very beginning of input string. See here regex101.com/r/feOUrE/1

Allan Over a year ago

I see didn't take into account this possibility! Thanks

MJ.Noori · Accepted Answer · 2019-03-10 09:10:05Z

0

you can use this (using |[.])(\w+)

Online demo

answered Mar 10, 2019 at 9:10

MJ.Noori

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1 Comment

revo Over a year ago

It potentially takes much more. Look here regex101.com/r/LHBjNo/5

Allan · Accepted Answer · 2019-03-10 09:53:45Z

0

You can use the regex:

(?<=^using\s)((?:\w+)(?:[.](?:\w+))*)(?=;)

input:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.IO;
using System.Text.RegularExpressions;

string something;
abc.something;
Console.WriteLine(".test.');

matches:

System
System.Collections.Generic
System.Linq
System.Text
System.IO
System.Text.RegularExpressions

then use the function on each match to extract each intermediate module:

$submodules= explode(".", $match);

demo:

https://regex101.com/r/p0K3dN/4/

Code sample:

$input="

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.IO;
using System.Text.RegularExpressions;

string something;
abc.something;
Console.WriteLine('.test.');

";

preg_match_all('/(?<=using\s)(?:\w+)(?:[.](?:\w+))*(?=;)/m', $input, $matches);

foreach($matches as $modules)
    foreach($modules as $module)
            print_r(explode(".",$module));

Result:

Array
(
    [0] => System
)
Array
(
    [0] => System
    [1] => Collections
    [2] => Generic
)
Array
(
    [0] => System
    [1] => Linq
)
Array
(
    [0] => System
    [1] => Text
)
Array
(
    [0] => System
    [1] => IO
)
Array
(
    [0] => System
    [1] => Text
    [2] => RegularExpressions
)

edited Mar 10, 2019 at 9:53

answered Mar 10, 2019 at 9:12

Allan

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4 Comments

revo Over a year ago

This is the same as @MJNBelief's answer.

Allan Over a year ago

@revo: Nice pick, I have answered to this question way too quickly. I have edited my answer now.

A.Ryshkov Over a year ago

It's not working using System.Collections.Generic; doesn't capture Collections

A.Ryshkov Over a year ago

I'm sorry, but i need namespaces to be already captured in regular expression, you just get all namespaces in one group

ElasticCode · Accepted Answer · 2019-03-10 16:17:27Z

0

Updated: The following regex

(?<=using\s)(\w*(?=[.;]))|\G(\w*(?=[;.]))

will give you result as below

(?<=using\s) Positive Lookbehind using and \s whitespace

(\w*(?=[.;])) matches any word character befor . or ;

\G asserts position at the end of the previous match.

(\w+(?=[.;])) repeat matches any word character befor . or ;

Check demo here

edited Mar 10, 2019 at 16:17

answered Mar 10, 2019 at 9:10

ElasticCode

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3 Comments

A.Ryshkov Over a year ago

Yeah, i add this note to my question

ElasticCode Over a year ago

@A.Ryshkov Updated

ElasticCode Over a year ago

@revo Thanks, Updated.

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