We use Roslyn to help speed up our query compilation process. However because Roslyn requires dot net 4.5 or higher, and our technology currently supports Dot Net 4.0, we have put the Roslyn Compiler interface into a separate DLL ( RosCompiler.dll )
If you are integrating IRDB.DLL into your own solution, and want to be able to use the Roslyn Compiler, you need to add the call RosCompiler.Setup() into your initialization code.
If you don’t the query compilation will use the older Dot Net 4.0 compiler query compilation that can take 70-120 ms per query, where as the Roslyn Compiler can run in 10ms or less.