Okay, that clarifies a distinction between struct and class, thank you. The referenced post directly addresses my use, although it’s still frustrating that I can’t express what I want.
From the client’s perspective, should BinaryReader be a struct or a class? I can make it a struct by passing the reader into the closure as an inout parameter. Doing so encourages me to make my read method an extension of BinaryReader, which make sense, until you get to readString(), which depends on a property of my class. That can be passed in as an argument, but either way it’s messier.
I’m not happy with any solution of these solutions, except maybe making it a class.