Quote Originally Posted by Shaggy Hiker View Post
You could add a constructor that takes an argument. If you do that, then the default constructor will be removed by the constructor and no default instance can be created because there won't be a constructor that takes no arguments.
Thanks, my class had already two constructors, and the one without parameters was quite an idle one. Removing it solved the problem. The parametrized constructor retrieves previous settings and, from now on, when there aren't any, I now send null values which are tested as they must. It works.

Quote Originally Posted by Shaggy Hiker View Post
However, does your method really belong in the form to begin with? It seems likely that it doesn't HAVE to be in the form, since it's a shared member. So, the easiest solution might be to move that method to a Module.
You are right. It does not have not to be in the form, but since it relates to nothing else than the data which is selected through that form, it sort of made sense to me this way. And it worked from day one, and now, thanks to your suggestion, I'm free of the warning that made me feel like there was something wrong.

Thank you very much!