February 5, 2010

Visual Studio Tip #2: Fear the Regex Magic No More

Here's a quick tip from the trenches.

I'm sure lots of developers had to - one day or another - weigh between replacing some text by hand or finding a regular expression to automate the process. Given that I'm not a regex master, it's often less time consuming for me to do it by hand for let's say a dozen of lines. Like our previous tip this is no new bleeding edge feature in VS but it's certainly often ignored.




Let's say you have a bunch of constants that you want to move into a config file where the variable name is the key and the value is... well the value. VS helps you compose your regex thanks to these little helpers:


Back to our constant:
private const string ftpLocation = "ftp://localhost/repository";

will be replaced as
<add key="ftpLocation" value="ftp://localhost/repository">

with this regex:
^([a-z ]*) {[a-zA-Z_]+} = "{[A-Za-z.\/\:\-]+}";

which is basically composed as follows:



^

select a new line



([a-z ]*)

select multiple characters composed of lowercase letters or space

private const string

{[a-zA-Z_]+}

select the next group of characters composed of letters or underscore
this group is replaceable: {}

ftpLocation

= "

followed by space - equals - quote

= "

= "

followed by space - equals - quote

= "

{[A-Za-z.\/\:\-]+}

select the next group of characters composed of letters or . or / (escaped) or : (escaped) or - (escaped)
this group is replaceable: {}

ftp://localhost/repository

";

followed by quote - semicolon

";



Don't forget to check the regular expression option on the find dialog.
You replace your selection by the desired format where you order your tag replacements:
<add key="\1" value="\2" />

Here's the final result on a replace all.



Of course this can be done in any Text Editor supporting regular expressions but be aware that the Visual Studio dialect differs a little from the usual standard.




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