To improve regeneration times, immediately before you install the .NET Framework 4 update, open an elevated command prompt and run the following commands.
Important Run these commands immediately before you apply the update. Otherwise, these commands are less effective.
On a computer that is running a 32-bit Windows operating system
On a computer that is running a 64-bit Windows operating system
%windir%\microsoft.net\framework64\v4.0.30319\ngen.exe update /force /queue