C# Regular expression search gives false

Question

I am trying to do a program that searches for certain tags inside textfiles and see if there is text in between those tags. Example of tags below.

--<UsrDef_Mod_Trigger_repl_BeginMod>
--<UsrDef_Mod_Trigger_repl_EndMod>

So i want to search for --<UsrDef_Mod_ and _Begin or _End

I made these RegExp, but i get false on every single one.

if (Regex.Match(line, @"/--<UsrDef_Mod_.*_BeginMod>/g", RegexOptions.None).Success)
else if (Regex.Match(line, @"/--<UsrDef_Mod_.*_EndMod>/g", RegexOptions.None).Success)

So any help to find where im going wrong. I have used regexr.com to check my regexp and its getting a match there but not in C#.

you can just try out yourself, e.g. here: http://regexstorm.net/tester. BTW Instead of Regex.Match(...).Success you may as well use Regex.IsMatch — CHS, Jun 02 '17 at 09:07
not trying to avoid the problem here, but a possible solution would be: line.substring(line.indexOf("-- — Gabri T, Jun 02 '17 at 09:11

H H · Accepted Answer · 2017-06-02T09:12:58.640

4

The .NET library Regex doesn't understand the "/ /g"wrapper.

Just remove it:

// Regex.Match(line, @"/--<UsrDef_Mod_.*_BeginMod>/g", 
   Regex.Match(line, @"--<UsrDef_Mod_.*_BeginMod>",

edited Jun 02 '17 at 09:12

answered Jun 02 '17 at 09:11

H H

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I just realized this myself by using the regexstorm.net/tester. After trying everything i removed them for the heck of it and it worked.. but thx. – Arto Uusikangas Jun 02 '17 at 09:12

Thrawn · Answer 2 · 2017-06-02T09:36:07.797

2

if (Regex.Match(line, @"--<UsrDef_Mod_.*_BeginMod>", RegexOptions.None).Success)
if (Regex.Match(line, @"--<UsrDef_Mod_.*_EndMod>", RegexOptions.None).Success)

Those both get a match - you just remove the /-- and /g options - As per Henk Holtermann´s Answer - a comparison of perl and c# regex options on SO - for further reference.

edited Jun 02 '17 at 09:36

answered Jun 02 '17 at 09:12

Thrawn

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The `/` delimiters should definitely not be used. – Hans Keﬆing Jun 02 '17 at 09:16

score 0 · Answer 3 · answered Jun 02 '17 at 09:26

var matches = Regex.Matches(text, @"<UsrDef_Mod_([a-zA-Z_]+)_BeginMod>([\s\S]+?)<UsrDef_Mod_\1_EndMod>");
if (matches != null)
    foreach (Match m in matches)
        Console.WriteLine(m.Groups[2].Value);

Group #2 will contain the text inside two tags.

C# Regular expression search gives false

3 Answers3