Interesting article. I have an interesting problem with the assemblies in ACAD 2017 using ObjectARX_2017 LINE 1: AcadAcCmColor aColor = new AcadAcCmColor(); LINE 2: aColor.ColorIndex = (AcColor)WIRE_COLOUR; LINE 3: line.TrueColor = aColor; All compiles Ok but LINE 2: produces a runtime error Exception thrown: 'System.Runtime.InteropServices.COMException' in mscorlib.dll Retrieving the COM class factory for component with CLSID {8489ED0D-5A6D-4C59-B173-2F9855DE496C} failed due to the following error: 80040154 Class not registered (Exception from HRESULT: 0x80040154 (REGDB_E_CLASSNOTREG)). I have my environment configured as suggested to 'embed' the assemblies. Any advice welcome Mark