Generally we require a internet connection to enable the Net-framework 3.5. Windows 8 already have this feature so no need to download it. Using this method you can enable Microsoft Net-framework 3.5 (Including 2.0, 3.0) Without Using Internet (Offline), Without Downloading Anything
Just Follow The Steps Below.
Windows installation disk or .iso File(say setup)
If you have .iso file just double click on it, it will be automatically mounted, If You have Installation disk insert it into your DVD writer/Reader (Do any one Not Both)
Now Search “cmd” and Run it as administrator (To run it as administrator right click on cmd and select “Run as Administrator)
And Type The Following Command In Cmd Dism.exe /online /enable-feature /featurename:NetFX3/SOURCE: G:sourcessxs /LimitAccess
After That When is 100% Complete Go to Control Panel (From Where You uninstall a program) There at right top side select “Turn On/Off Windows Feature” (See Image Below)
5.) Now Enable Net-framework 3.5 From Here (See image Below)