c# - Why do you have to mark a class with the attribute [serializable]?

Question

Seeing as you can convert any document to a byte array and save it to disk, and then rebuild the file to its original form (as long as you have meta data for its filename etc.).

Why do you have to mark a class with [Serializable] etc? Is that just the same idea, "meta data" type information so when you cast the object to its class things are mapped properly?

Answer 1

Binary serialization is pretty powerful, it can create an instance of a class without running the constructor and can set fields in your class that you declared private. Regular code can of course not do this. By applying the [Serializable] attribute, you explicitly give it the go-ahead to mess with your private parts. And you implicitly give that permission to only the BinaryFormatter class.

XML serialization doesn't need this kind of okay, it only serializes members that are public.

DataContractSerializer can serialize private members as well. It therefore needs an explicit okay again, now with the [DataContract] attribute.