Replace commas enclosed in curly braces (but not quite) - regex

Question

This seems to be a duplicate question of an already asked one but not really. What I'm looking for is one or more regular expressions without the help of any programming language to change the following text String.Concat( new string[] { "some", "random", "text", string1, string2, "end" }) into "some" + "random" + "text" + string1 + string2 + "end".
I was thinking of using two regular expressions, replacing the commas with pluses, and then removing the String.Concat( new string[] { ... }). The second part is quite easy, but I am struggling with the first regular expression. I used a positive look-behind expression, but it matches only the first comma: (?<=String\.Concat\(new string\[\] \{[^,}]*),
I'm not an expert but I think that this is a limitation of the regular expression engine. Once the first comma is matched, the regular expression engine moves the starting matching index after the comma and it doesn't match anymore the look-behind group before it.
Is there a regular expression to make this substitution, pluses instead of commas, without the help on any programming language?

Answer 1

Just like you said: first replace all comma by plus signs:
Regex 1: /,/g
Replacement 1: " +"
Then remove all unnecessary stuff, capture what you need and use a backreference to the captured group as replacement:
Regex 2: /String\.Concat\(\s*new\s*string\s*\[\]\s*{\s*(.*?)\s*}\)/g
Replacement 2: "$1"(or however you can specify backreferences).

Answer 2

I'm assuming you're using a text editor:
,
substitution:
+
See the demo
Second:
.*?{(.*?)}.*
Replacement
$1
See the demo

Answer 3

You should do it in two steps.
First substitution
s/^\s*String\s*\.Concat\s*\(\s*new\s+string\[\]\s*\{\s*("[^\}]*")\s*\}\)\s*$/$1/i
gets you
"some", "random", "text", string1, string2, "end"
Second one
s/\s*("[^"]*"|\b\w+\b)\s*,\s*/$1 + /g
returns your desired output
"some" + "random" + "text" + string1 + string2 + "end"
Check this: https://ideone.com/QuRKmt (sample code in Perl).

Answer 4

Update Notepad++ single pass solution
(Note you can also do this in RegexFormat8 using the Boost extended replacement option)
Find (?:String\.Concat\(\s*new\s*string\s*\[\]\s*{\s*([^,})]*?)\s*(?=,|}\))|\G(?!^)\s*,\s*([^,})]*?)\s*(?=,|}\)))(?:}\)|(?=(?:\s*,\s*[^,})]*)+}\)))
Replace (?1$1: + $2)
(without conditional replace its + $1$2 https://regex101.com/r/Vqe44r/1)
Formatted-expand mode
(?:
String \. Concat\( \s* new \s* string \s* \[\] \s* { \s*
( [^,})]*? ) # (1)
\s*
(?= , | }\) )
|
\G
(?! ^ )
\s* , \s*
( [^,})]*? ) # (2)
\s*
(?= , | }\) )
)
(?:
}\)
|
(?=
(?:
\s* , \s*
[^,})]*
)+
}\)
)
)
Output
"some" + "random" + "text" + string1 + string2 + "end"