c# Reflection CompileAssemblyFromSource slow

I've some problems with reflection:

In my code I dinamically load c# code from database, compile it and load some object from that library. All that works, but the compilation made by CompileAssemblyFromSource is very very slow (about 60s).

I tried to compile the same c# code with Visual Studio 2015 and the build phase took less than 1s...

What's wrong? Is CompileAssemblyFromSource so slow?

Thank you for your help.

Matteo