Remove a string after a certain character('_')?

Question

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I have a filename, i.e., "B1_1-A.dwg".
I want this to appear as "B1" in a report that I am creating.
I an the report editor there is an option to write a code in c#.
Bt condition is that the code should be written in a single line.
Please provide some solution.

What I have tried:

I tried substring and split but I am not very good at c# so I am not sure whether I have written a correct code or not.

Posted 20-Feb-18 17:38pm

Manav Singh Chauhan

Updated 22-Feb-18 18:32pm

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Comments

PIEBALDconsult 20-Feb-18 23:56pm

Well, show us the code. Does it work?

phil.o 21-Feb-18 8:41am

Please see my updated answer which now matches the substring properly.

BillWoodruff 21-Feb-18 10:38am

"I am not very good at c#" So, start studying and experimenting instead of acting helpless.

3 solutions

Solution 2

You can use a regular expression for that.
Something like

C#

using System.Text.RegularExpressions;
// ...
private static readonly Regex r = new Regex(@"_.*", RegexOptions.Compiled | RegexOptions.CultureInvariant);
// _.? means "underscore character, followed by zero or more character"
// ...
string filename = "B1_1-A.dwg";
filename = r.Replace(filename, "");
// Here, filename is "B1"

Note: if you are using the regular expression repeatedly, it is probably best to make it a static readonly field in the class you are using it, because creating a regex repeatedly impacts the expected performance; if you make it static, the performance will be much higher.

Second version using static Replace method:

C#

using System.Text.regularExpressions;
// ...
string filename = "B1_1-A.dwg";
filename = Regex.Replace(filename, @"_.*", "");
// Here, filename is "B1"

[Edit] My bad, I misread the question. Should not answer before my second coffee, it seems. I modified the solution. [/Edit]

[Edit2] Tested it; does not match. Still searching [/Edit2]

[Edit3] Now working. Weird that it matches with * but not ?. [/Edit3]

Posted 20-Feb-18 23:13pm

phil.o

Updated 21-Feb-18 2:40am

v9

Comments

PIEBALDconsult 21-Feb-18 6:25am

There's no such thing as a "line of code".

Sarita Mall 21-Feb-18 23:51pm

I think my answer was right,which i deleted.
My Answer which i have written earlier :

filename.Split('_')[0];

phil.o 22-Feb-18 5:40am

Yes, it was; if you would mind adding it back again it would be credited.

PIEBALDconsult 21-Feb-18 6:25am

Or use the static method on the Regex class -- it provides performance improvements too.

phil.o 21-Feb-18 8:12am

Are you t alking about static Replace and its overloads? I always wondered whether or not corresponding regex is constructed at each call, that's why I used to prefer defining a static variable. I must confess I have never conducted any test, though.
Thanks for the highlight.

PIEBALDconsult 21-Feb-18 8:26am

I had been working on my own Regex caching scheme but found it didn't work well in some cases.
It wasn't until a few weeks ago that I noticed this in the documentation:
"This regular expression pattern is cached for rapid retrieval by the regular expression engine."
So now I am prefering the static methods, particularly when parallelism is paramount.

phil.o 21-Feb-18 8:42am

I think I will revise my scheme too. Thank a lot!

Maciej Los 21-Feb-18 9:20am

5!

phil.o 21-Feb-18 9:23am

Thanks. I think your solution is simpler, though (thus, better). At first, I misread the question and it made sense to use a regex.

Maciej Los 21-Feb-18 9:32am

Every solution is good ;) I've seen your answer earlier and i was wondering why entire content has been striked. Seems, your regex pattern was wrong.

phil.o 21-Feb-18 9:42am

Indeed, I striked it while I was searching for proper expression.
I cannot figure out why _.* matches, whereas _.? does not.

Maciej Los 21-Feb-18 10:47am

;) An explanation is quite obvious:

* 	Matches the previous element zero or more times.
? 	Matches the previous element zero or one time.

See: MSDN documentation

phil.o 21-Feb-18 10:55am

* digging *
* digging *
* hiding *
what a shame! :)

Maciej Los 21-Feb-18 10:59am

;)

Solution 4

Hi ,

This is the solution which i deleted earlier.

filename.Split('_')[0];

please let me know if it not fulfill the requirement.

Regards,
Sarita

Posted 22-Feb-18 18:33pm

Sarita Mall

Updated 22-Feb-18 18:34pm

v2

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Maciej Los · Accepted Answer · 2018-02-21T02:43:00

Quote:
I have a filename, i.e., "B1_1-A.dwg".
I want this to appear as "B1"

Not sure what is the problem... Take a look at example:

C#

string filename = "B1_1-A.dwg";
int pos = filename.IndexOf("_");
string newfilename = filename.Substring(0, pos);
Console.WriteLine(newfilename);//prints: B1

Above code can be simplified to:

C#

filename.Substring(0, filename.IndexOf("_"));

In case i misunderstood your requirements, please, let me know.