I am trying to (programatically) find references to a specific string i.e. \'LOCK_ID\' within a large number of VB6 files. To help people navigate directly to the reference
there are a number of tools to do this. I'll list them in edit as I think of them. The first to come to mind is TextPad (menu: search / search in files)
Second tool: UEStudio.
Both of these are paid tools. There are trials, they are quick to install, etc.
Failing that, you could install Cygwin for some Linux style grep functionality.
Q&A to comments
in that case load the file in, split it on "\n", keep a counter, and do the search yourself -- probably with RegEx regular expression.
... there is a cool LINQ Expression here (you just need the where portion): Linq To Text Files
Work with the directory class recursively to catch all files.
http://www.dotnetperls.com/recursively-find-files