How to install .Net 3.5?

under Win8 Windows8 system integration is .Net4.5, but many software operations require Microsoft.Net3.5 to run, but can not be successfully installed using the system's own upgrade function. In fact, Windows8 installation files have been integrated with .Net3.5
1. At this time, you only need to use the virtual CD-ROM to load the ISO file of Windows8.
2, then start the command prompt as administrator and enter dism.exe/Online/enable-feature/featurename:NetFX3/Source:H:sourcessxs and press Enter (where H: is the virtual drive letter, please refer to the changes yourself). When the screen prompts "Operation completed successfully", you can install .Net3.5 normally.