Perfect strategy for installing .Net3.5 under Win8

When running a program written in .Net version (below 4.0) in Win8, you will be prompted to install .Net 3.5. However, if you use online installation, you will not succeed. Online upgrade will encounter error 0x800F0906. Obviously Win8 system integration is .Net4.0, but a lot of software running requires Microsoft.Net3.5 to run, using the system's own upgrade and can not be installed properly, which can make many friends wonder.
In fact, we do not need to install on the Internet. The Win8 installation file has integrated .Net3.5. In this case, you only need to use the virtual CD-ROM to load the ISO file of Windows8, then start the command prompt as administrator and enter dism. Exe/online/enable-feature/featurename:NetFX3/Source:H:\\sources\\sxs (Figure 1) and press Enter (where H: is the virtual drive letter, please refer to the changes). When the screen prompts "Operation completed successfully" (Figure 2), you can install .Net3.5 normally.
Figure 1 Figure 2
After a little waiting, we have finished executing. Once we open the Add/Remove windows function, we can find that our .Net 3.5 has been installed successfully. It seems that the built-in version of .Net is too new. In exchange for the old version of .Net3.5, you can reinstall some old software.