FileStream is not marked as serializable, but the whole class is?

Question

I have a class definition in separate assembly. The class is marked as serializable:

namespace example
{
    [Serializable]
    public class my_class
    {
        public List<string> text;
        public FileStream audio;

        public Image img;
        public string nickname;
    }
}

I can load this assembly and create an instance of this class with no problem. But when i try to cast to byte[] using code bellow

private byte[] ToByteArray()
{
    if (send == null) // 'send' is a my_class instance;
        return null;

    BinaryFormatter bf = new BinaryFormatter();
    bf.Binder = new Binder();
    bf.AssemblyFormat = System.Runtime.Serialization.Formatters.FormatterAssemblyStyle.Full;
    bf.Binder.BindToType(example_assembly.FullName, "my_class");
    MemoryStream ms = new MemoryStream();
    bf.Serialize(ms, send);
    return ms.ToArray();
}

i get:

System.Runtime.Serialization.SerializationException -> Type System.IO.FileStream in Assembly 'mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089' is not marked as serializable.

I don't understand this because whole class is marked as serializable. Any sugestions ??

Answer 1

The Serializable attribute simply indicates a class can be serialized. It does not change the underlying functionality of a class. You can mark non-serializable classes and members as serializable.

A FileStream is not serializable. Marking it as such will not change that.

http://msdn.microsoft.com/en-us/library/system.serializableattribute(v=vs.110).aspx

Answer 2

Members are serializable, but their types should also be serializable. FileStream is not. You can implement ISerializable interface in your class and manully serialize audio/img fields.

Answer 3

The problem is that my_class is decorated with the [SerializableAttribute], but the class FileStream is not. =/

You can skip the property serialization by decorating the FileStream property with a [NonSerializedAttribute], but you can't serialize a file Stream.

This is not very beautiful, but this guy here and here converted the stream to a string. You could control the serialization of your class by implementing the ISerializale interface and parse the FileStream to something that is Serializable.