While you are installing an Office Web Apps Server 2013 for your Skype for Business deployment you received the following error during installation:
"Setup is unable to proceed due to the following error(s): This product requires Microsoft .Net Framework 4.5"
You now started to troubleshoot the issue:
1.) Make sure that you installed all the prerequisites:
which also included the 4.5 .net Framework
2.) Now check which .net Framework you have installed (more infos here) via:
Get-ItemProperty -Path “HKLM:SOFTWARE\Microsoft\NET Framework Setup\NDP\v4\Full” | Format-List Release
If that shows a version higher then 4.5 you might have already run Windows update and during this you installed a .net Framework and updated it to 4.6.
A solution which worked for me was to uninstall the following updates:
For .NET Framework 4.6.1 we removed the following KB: KB3102467
For .NET Framework 4.6 we removed the following KB: KB3045563
After they where removed and after a reboot from the OS was initiated I was able to install Office Web Apps Server 2013 without any issues.
Please keep noted that the .NET Framework version 4.6 and higher includes a new Just-In-Time (JIT) compiler which might cause issues with your MS Office Web Apps Server 2013 deployment. Microsoft mentioned here to disable that via:
Then, add the following:
Value name: useLegacyJit
Type: DWORD (32-bit) Value (also called REG_WORD)
When using .net Framework version 4.6 with Office Web Apps Server 2013
Keep noted that using .NET Framework 4.6 might also prevent you from updating/patching MS Office Web Apps Server 2013, so a good option might be currently to block the .NET Framework version 4.6 from being installed via Windows updates as explained here.