FindInFiles is an Open Source app geared at developers capable of searching text in sources.
It uses the context menu to assist in finding text within files contained in a folder. It then allows you to edit it in an external editor like any of those listed below. FindInFiles requires specific search parameters to be entered for it to work. There is an unpropagated dropdown that you will need to enter the file types within. You then need to drag n' drop the folder you wish to search and hit the find button. Depending on the parameters, the search time will vary. It can also be initiated from the context menu.
FindInFiles is a viable search tool wrapped in a sparse UI, making it easy to use. But it may not be the best first choice for a novice user.