First time with this error - Inconsistent accessibility

Question

This is my first time working with interfaces and proper namespace structure. When I compile I get the error below, I have no idea what it means. Any searches I do shows up

Answer 1

IOperatorRequest is internal which is less accessible than public.

Top-level types, which are not nested in other types, can only have internal or public accessibility. The default accessibility for these types is internal.

from MSDN

Answer 2

You have a public property on a public class that exposes a list of non-public types.
You need to change IOperatorRequest to be public or change the UrlBuilderO2 class or GetUrlReuests method to be non-public.

Answer 3

The problem is IOperatorRequest is probably internal.

UPDATE

What I said is correct. Omitting modifier makes it internal.

Classes and structs that are declared directly within a namespace (in other words, that are not nested within other classes or structs) can be either public or internal. Internal is the default if no access modifier is specified.