Regex in the IDE


Since I understood how complicated, slow and troublesome regular expressions can be, I always tried to solve my programming problems (ekhm… challenges) without them. But some time ago, when I get involved into refactoring of huge banking system, I realized that this is not the case anymore. Regex can be very useful in certain cases…

The purpose of this note is to notify others that regex can be useful while working with the code and to hold all my most useful regex tips.

Use case

I have an SQL query and I’d like to create variables based on them. What to do? Of course, I can do it manually. I can also use regex 😛

I’d like to modify the SQL query from the orange ellipsis into the form shown in the green ellipsis. It can be easily done using regex… almost.

At the first glance, it is not an easy task. First, I will copy the SQL into the foreach loop.

The top-red rectangle encloses controls shown after CTRL+H was pressed. Don’t forget to select blue-rectangle-enclosed-regex-button.

So, I copied SQL, selected it, pressed CTRL-H and clicked the asterisk button that enables regex in the search&replace action. Now the trickiest part – what do I want to replace with what?

Search text box: \$.*Print(.*)\.(.*)\).*

Replace text box: var \l$2 = row.GetCellValue(nameof(Print$1.$2));

What does it mean? The heart of the regex above is the group feature. It means that the group found by regex can be used in the replacement statement. Groups are enclosed by parenthesis and indexed starting from 1. Then, in the replacement, it can be referred to with the dollar sign.

After the above was applied, the selection changed to:

SQL magically changed to variables assignment. Note that only one method is invoked on the record object. This is a quite significant restriction.

The replacement string refers to the groups found by the regex:

\l is a special modifier that will be explained below

This example shows how to use regexes in the IDE. For such small changes, regex seems kinda like shooting a fly with a cannon, but it’s worth considering when we work with the bigger files. Especially with the „magical recipies”:

„Magical recipies”

I found them here, if you like it, give a kudos!

Capitalize words
Find: (\s)([a-z]) (\s also matches new lines, i.e. „venuS” => „VenuS”)
Replace: $1\u$2

Uncapitalize words
Find: (\s)([A-Z])
Replace: $1\l$2

Remove camel case (e.g. cAmelCAse => camelcAse => camelcase)
Find: ([a-z])([A-Z])
Replace: $1\l$2

Lowercase letters within words (e.g. LowerCASe => Lowercase)
Find: (\w)([A-Z]+)
Replace: $1\L$2
Alternate Replace: \L$0

Uppercase letters within words (e.g. upperCASe => uPPERCASE)
Find: (\w)([A-Z]+)
Replace: $1\U$2

Uppercase previous (e.g. upperCase => UPPERCase)
Find: (\w+)([A-Z])
Replace: \U$1$2

Lowercase previous (e.g. LOWERCase => lowerCase)
Find: (\w+)([A-Z])
Replace: \L$1$2

Uppercase the rest (e.g. upperCase => upperCASE)
Find: ([A-Z])(\w+)
Replace: $1\U$2

Lowercase the rest (e.g. lOWERCASE => lOwercase)
Find: ([A-Z])(\w+)
Replace: $1\L$2

Shift-right-uppercase (e.g. Case => cAse => caSe => casE)
Find: ([a-z\s])([A-Z])(\w)
Replace: $1\l$2\u$3

Shift-left-uppercase (e.g. CasE => CaSe => CAse => Case)
Find: (\w)([A-Z])([a-z\s])
Replace: \u$1\l$2$3

The end

That’s it. As I said, I hope that this note will inspire you to at least give regex a try. I started to use it and if I find something useful, I will add it to this page. The magical recipes listed above are a good start, we can do a lot with them.

I almost forgot. I use Rider & Visual Studio 2022. Sometimes IDE differs slightly when comes to regex handling. If the examples don’t work for you, look here.

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