Mscorsvw.exe using 50 % of my CPU

mscorsvw.exe is precompiling .NET assemblies in the background. Once it's done, it will go away. To speed up the process run:

ngen.exe executequeueditems

From C:\Windows\Microsoft.NET\Framework64\v4.0.30319 or different .NET installation directory accordingly. 
I had the problem on Windows 2012 server with RDS session configuration.