http://www.csharp-station.com/
http://www.tutorialspoint.com/csharp/
http://www.techrum.vn/threads/hoc-c-co-ban-cho-nguoi-moi-bat-dau-bai-10-tao-va-goi-cac-helper-method-don-gian.13233/#post-73091
http://iceteaviet.blogspot.com/2015/07/hoc-c-thi-bat-au-tu-au.html
