Question

I’m trying to find a String in a Textfile. I’m using the RegEx Method for that. But I need to get the Previous String, which is existing before the found String, as Method Output. How can i do it with c#? Can anyone give me some Idea?

For Example:
In that Textfile is a Line with 'routerbl router0000;'
I’m searching 'router0000;' and if i find 'router0000;' then i want to get 'routerbl'.

Answer 1

You have two possibilities

1. Match what you want using a capturing group, something like this

   (\S+)\s+router0000
   

   and you will find your result in the capturing group 1

2. Match your pattern and ensure the following string with a lookahead

   \S+(?=\s+router0000)
   

   this will match only the part you want.