Hello!!
1.Dev  Bhoomi institute of polytechnic

2.DIT University

3.Graphic Era Hill university

4.Quantum school of technology

5.SRHU

6.Himgiri Zee University

7.BFIT group of institutions

8.Guru Ram Das  institute of management and technology ..these are some of   the colleges in dehradun to do diploma in computer science engineering.Hope this may helps you.

Thank you!!