How can I deserialize an interface type?

Question

I serialize a class which includes a property called Model as IModel but when I try to Deserialize it I'm getting the following exception:

System.Runtime.Serialization.SerializationException: Type 'MYN.IModel' in Assembly 'MYN.Defs, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null' is not marked as serializable.

It's binary serialization. Model marked as serializable. Obviously IModel is not.

So what's the solution, what am I doing wrong? Why does it try to seriliaze or deserialize an interface anyway?

P.S. Interface hasn't got an Enum in it.

Answer 1

Hi,

Probably you need to expose those property implicitly within your class:

instead of IModel.Model property add

public MyClass Model

Answer 2

It makes sense to get that error, because an IModel property could refer to different classes and there is no guarantee that they are all Serializable.

---

OK, I gave it a try and we have:

Testcase error, it works on my computer.

interface IFoo { }

[Serializable]
class CFoo : IFoo   { }

[Serializable]
class Bar
{
    public IFoo Foo { get; set; }
}

And Bar Serializes and Deserializes fine.

Bar b = new Bar();
b.Foo = new CFoo();

using (var s = new System.IO.MemoryStream())
{
    var bf = new System.Runtime.Serialization.Formatters.Binary.BinaryFormatter();
    bf.Serialize(s, b);
    s.Position = 0;
    b = (Bar)bf.Deserialize(s);

    Console.WriteLine("OK");
}

So, what is different from your IModel and Model?

Answer 3

I'm fairly sure that you can't serialize/deserialize interfaces, only instances of classes. I can't find any documentation to confirm this, but I recall trying to do the same thing without any success.

You could try using an abstract base class instead of an interface, but I haven't tried that.

Answer 4

I suspect it's because during deserialization it initiates a new instance of the class and then copies the data into it. It can't new an interface so the deserialization can not be completed. This is why you need a constructor that takes no arguments for serialization.

Not sure on the solution, I've never worked that bit out. I'd probably override the class and inherit the property with a concrete type then serialize that.