To search for a pattern across all project files, or other non-project files, use the Search Files command. See also “Search Files”. The Search Files command is similar to the Search command, except you can specify what files you want to search. The results of the search are placed in the Search Results window. The search results also contain hidden information called source links.
If you are just looking for single, whole-word references across your whole project, the Lookup References command is much faster. See also “Lookup References”.