To Joe's point... You rarely should locally install and run the source of DNN. I've been building DNN solutions and extensions since the beginning, and I only run the source of it when I'm actually preparing to submit a pull request to it. The rest of the time, the source is simply in another folder, just in case I want to dig into the source code to research something.
Instead, you should be building your own DNN extensions against and tested against an "install" version of DNN. You can get a guided tour of the DNN environment and the development environment from DNNDocs.com.