When extracting interface of a Form class with some properties having designer attributes (e.g. Browsable or DesignerSerializationVisibility), the extracted property in the interface, will have these attributes too. here's what I got : public interface ICompanySubForm { [Browsable(false)] [DesignerSerializationVisibility(DesignerSerializationVisibility.Hidden)] CompanyModule Owner { get; } } furthermore, the extracted interface is places in the .Designer file (for the Form) which is better if it is placed under the same .cs file.