Thank you very much for your advise about including object into column class. I didn't think of it myself :-) Now it works fine.

As for including MemberClassLibrary in Column class I consider it's rather possible. When you drop Grid object to your form and set ColumnCount to value other than 0 it inserts the default Text objects into Columns. Why not to get the first found TextBox-based class definition from my class library or generate error message otherwise?