Please see my comment.
I mean, on second though, I can share a very beneficial coding style, when it comes to implementing some interfaces, especially good with forms. This style is based on the fact that
partial class declaration requires each element in the list of base classes or interfaces only once. It means, you should not to repeat any of them. This gives you the opportunity to separate different aspects of the class. In particular, the parts related to implementation of each interface, could be in separate files. Like this:
public partial class MyForm : System.Windows.Forms.Form { }
internal interface IFirst { }
internal interface ISecond { }
public partial class MyForm : IFirst { }
public partial class MyForm : ISecond { }
—SA