Question

I need regular expression to validate text for all words in text must be unique.
for example my text will be like

valid text->
“Advance|Paid|Regular|Next”

Invalid text->
“Advance|Paid|Paid|Regular|Next|Advance”

words are not fix it can be any thing.

Please help me how I can achieve it in .net

Answer 1

Yeah, it is possible using backreferences:

(?:^|\|)([a-z]+)\|.+\|\1(?:\||$)

That will match expressions with repeated words, with the first instance of the word as a group. Either negate it to see if words are repeated, or use a replace to remove the words.

To use spaces instead of |:

\b([a-z]+)\b.+\b\1\b