Solving Installation Problems with .NET 3.5 on Server 2012 R2

If you're trying to install .NET 3.5 on Windows Server 2012 R2, you're probably going to run into an installation issue. The easiest way to solve this is to ensure you have Windows installation media available and use the command below rather than the add/remove features GUI or standalone .NET installer.

dism /online /enable-feature /featurename:NetFX3 /all /Source:w:\sources\sxs /LimitAccess

replace the drive letter "w" with your windows installation media path.