Hi there this is not installing it but it seems to allow programs that require it to work.
1) Copy all frameworks from the windows folder of an actual windows install. ( C:\windows\Microsoft.Net\Frameworks\ )
2) Place in the same folder in your windows bottle.
3) Export the .net values from the windows registry. (HKEY_LOCAL_MACHINE/SOFTWARE/MICROSOFT/.NET/)
4) Import into the botttles registry (Use the run command to open regedit the same way as in windows).
5) Install Mono (to run .net executables wine still needs this).
6) Install software that needed it and use.