I have a VB6 application and it needs to be binary compatible with the old dll. While building the project in command line, the build is succeeded. If any method definitions were changed (like parameter change), the build is not succeeded in command line. When I try it from IDE, it prompts a warning message asking an option to preserve compatibility, if it is selected, and then the build is succeed. Please let me know how to make the preserve compatibility option from command line.