Question

I need to serialize a class C using BinaryFormatter.

So I mark C as [Serializable].
C inherits an abstract B class.

B is NOT marked as [Serializable].
B inherits A class,

A is [Serializable] and also it implements ISerializable;

What situation can we have?

AProperty will be serialized
BProperty will not be serialized (?)
CProperty will be serialized

Answer 1

Your edit changes everything; if A implements ISerializable then they all implement ISerializable. With that, you are using custom serialization so the behaviour is determined entirely by the GetObjectData and serialization-constructor code you write in each of A / B / C.

---

Original answer, when there was no mention of ISerializable

serialization is generally based on type of the actual object at runtime, and BinaryFormatter (which maps to [Serializable]) is a field serializer. However, if B is not marked [Serializable], it cannot be serialized with BinaryFormatter (unless it is ISerializable); so:

• if it is an A, all A fields will be serialized
• if it is a C, it will throw an exception
• (it can’t be a B since that is abstract; but if it was, that would throw too)

If you aren’t using BinaryFormatter (and personally I don’t think BinaryFormatter is a good choice most of the time), then the behaviour will depend on the specific serializer.

My advice: use a different serializer; there are plenty. Almost all are (IMO) better choices than BinaryFormatter.