c# - Exclude starts with but include ends with -

i can't figure out myself, have match string starts asp. , ends _aspx, need exclude start of match (the asp. part).

for example,

 string input = "random stack trace text asp.filename_aspx random text";  regex r = new regex("regular expression needed!!!");   var mc = r.matches(s);          foreach (var item in mc)         {             console.writeline(item.tostring());         } 

and have needs output this,

filename_aspx

that's job positive lookbehind assertion:

regex r = new regex(@"(?<=\basp\.)\s+_aspx"); 

(?<=\basp\.) ensures asp. present before starting position of match, doesn't include in match result. \b word boundary anchor asserts don't match wasp, asp.

\s+ matches 1 or more non-whitespace characters (this assumes filenames don't contain spaces).