Connect to different version of AutoCAD

[BestFriendCZ]

I have a computer where are installed two version of ACAD (2017/2020). There is external app which connects to ACAD. This APP has DLL from ACAD version 2017.

If is ACAD 2017 running and so

acadApp = (AcadApplication)Marshal.GetActiveObject("Autocad.Application");   - isn't null

acadApp = (AcadApplication)Marshal.GetActiveObject("Autocad.Application.21.0");   - isn't null

acadApp = (AcadApplication)Marshal.GetActiveObject("Autocad.Application.23.1");   -  null !!!!

If is ACAD 2020 running and so

acadApp = (AcadApplication)Marshal.GetActiveObject("Autocad.Application");   -  null

acadApp = (AcadApplication)Marshal.GetActiveObject("Autocad.Application.21.0");   - null

acadApp = (AcadApplication)Marshal.GetActiveObject("Autocad.Application.23.1");   -  null !!!!

when I connect to this app DLL from version 2020 and ACAD 2020 running

acadApp = (AcadApplication)Marshal.GetActiveObject("Autocad.Application");   -  isn't null

acadApp = (AcadApplication)Marshal.GetActiveObject("Autocad.Application.21.0");   - null

acadApp = (AcadApplication)Marshal.GetActiveObject("Autocad.Application.23.1");   -  isn't null

DLL which is used

Autodesk.AutoCAD.Interop

Autodesk.AutoCAD.Interop.Common

I would like to know if exist any way how to connect to different versions of AUTOCAD. I mean doesn't matter which version running just connect to running instances

[_gile · Accepted solution]

Hi,

The COM libraries (Autodesk.AutoCAD.Interop and Autodesk.AutoCAD.Interop.Common) are version dependant. That means you must reference the 2017 libraries if you target AutoCAD 2017 and the 2019 or 2020 libraries if you target AutoCAD 2020.

One way to get rid of version dependence is to use late binding with the 'dynamic' type but this will make you lose the advantages of strong typing (intellisense and error detection at edition time).

dynamic acadApp = Marshal.GetActiveObject("Autocad.Application");

But, assuming AutoCAD is already runing, why not using the .NET API with a standard plugin (i.e. a DLL to be netloaded in AutoCAD)?

In my opinion, as far as you can, avoid using AutoCAD.Interop.

[BestFriendCZ]

Hi gile,

Thanks for your advice. I understand that use COM API is hell but on our company are lots of old Apps which using this type of API (thousand and thousand lines spaghetti code) and i have to support this old Apps too somehow…