mono --version

Mono JIT compiler version 4.6.1 (mono-4.6.0-branch-c8sr0/abb06f1 Fri Sep 23 19:24:23 EDT 2016)
Copyright (C) 2002-2014 Novell, Inc, Xamarin Inc and Contributors. www.mono-project.com
	TLS:           normal
	SIGSEGV:       altstack
	Notification:  kqueue
	Architecture:  x86
	Disabled:      none
	Misc:          softdebug
	LLVM:          yes(3.6.0svn-mono-master/8b1520c)
	GC:            sgen

System.TypeInitializationException: The type initializer for 'Db.Mongo' threw an exception. ---> System.TypeInitializationException: The type initializer for '<StartupCode$Kraken>.$Db.Mongo' threw an exception. ---> System.DllNotFoundException: ntdll.dll
  at (wrapper managed-to-native) Interop+NtDll:RtlGetVersion (Interop/NtDll/RTL_OSVERSIONINFOEX&)
  at Interop+NtDll.RtlGetVersion () [0x0001a] in <dd91439f3167478ebd2cbf9c036a1395>:0 
  at System.Runtime.InteropServices.RuntimeInformation.get_OSDescription () [0x00007] in <dd91439f3167478ebd2cbf9c036a1395>:0 
  at MongoDB.Driver.Core.Connections.ClientDocumentHelper.CreateOSDocument () [0x00042] in <44d1ee4d649846bda18b2609a70d66b9>:0 
  at System.Lazy`1[T].CreateValue () [0x00075] in <dca3b561b8ad4f9fb10141d81b39ff45>:0 
   --- End of inner exception stack trace ---
  at (wrapper managed-to-native) System.Object:__icall_wrapper_mono_generic_class_init (intptr)
  at Db.Mongo..cctor () [0x00000] in <5862ad762f76149ea745038376ad6258>:0