Perguntas de entrevista de vagas de C# Software Engineer da empresa IntegriDATA

I was given a take home coding test. After finished and passed, I was scheduled by a webext interview. The guy gave me a bunch of codes looks like the source files in one of their projects. I wonder if he use me as a free worker to solve some problems. Unpleasant experience because the questions are all tough, rarely used and tricky ones.