The AutoCAD .NET API is a cross implementation of ObjectARX and ActiveX Automation. While you can access ActiveX Automation from ObjectARX, .NET API makes working with the two rather seamless. As you work with objects using the native .NET API, you can access the equivalent COM object from a property. In some cases, the COM object is the only way to access an AutoCAD feature programmatically. Some examples of properties that expose COM objects through the .NET API are, Preferences, Menubar, MenuGroups, AcadObject and AcadApplication.

The Preferences property of the Application object provides access to a set of COM objects, each corresponding to a tab in the Options dialog box. Together, these objects provide access to all the registry-stored settings in the Options dialog box. You can also set and modify options (and system variables that are not part of the Options dialog box) with the SetSystemVariable and GetSystemVariable methods of the Application object. For more information about using the Preferences object, see the ActiveX and VBA Developer’s Guide.

Accessing COM objects is useful if you are working with existing code that might have been originally developed for VB or VBA, or even when working with a third-party library that might work with the AutoCAD ActiveX Automation library with the .NET API. Like the Preferences object, you can also access utilities which translate coordinates or define a new point based on an angle and distance using the Utility object which can be accessed from the AcadApplication COM object which is the equivalent of the Application object in the .NET API.