Thank you, Juergen, I really appreciate you help
I have now attached DcadExp25x64.dll in MVS 2019 as reference. But as you can see from the attached snap shot DesignCAD.Application is not defined. The definition: DcApp=DesignCADApplication_definst.Application comes from an earlier version of Visual Studio and DesignCAD.
Do you know how to make a correct definition so I can have my program compiled and working? The bin-folder in Solution Explorer have files which comes from an earlier version of Visual Studio and DesignCAD.