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No, but you can have a class inside a class, is that what you mean?
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Hi!
I just stumbled over an unexpected behaviour when trying to serialize a derived class using a BinaryFormatter, I guess the best is to show in code:
Animal a = new Animal();
Dog d = new Dog();
Animal dogAsAnimal = d as Animal;
BinaryFormatter bf = new BinaryFormatter();
bf.Serialize(serializationStream, a);
bf.Serialize(serializationStream, dogAsAnimal); I can't really understand why the last line is trying to serialize the object as Dog instead of Animal - is there any way to keep BinaryFormatter from doing this (short of adding a copy constructor to Animal and actually creating a new object)?
Thanks in advance!
Regards,
mav
--
Black holes are the places where God divided by 0...
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bf.Serialize(serializationStream, (Animal) d); ?
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It doesn't matter whether I use as or an explicit cast.
In the real code I had a method ToFile(Animal a, string path) and it also showed the effect.
The debugger does show that it's an Animal reference in every case.
Regards,
mav
--
Black holes are the places where God divided by 0...
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The derived class also has to be serializable.
I think you'll also find that only protected and public vars will be serialized from the base class, but I'm just guessing at that.
"Why don't you tie a kerosene-soaked rag around your ankles so the ants won't climb up and eat your candy ass..." - Dale Earnhardt, 1997
-----
"...the staggering layers of obscenity in your statement make it a work of art on so many levels." - Jason Jystad, 10/26/2001
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But that's something I explicitely do not need/want. Of course I could flag Dog as Serializable, too, but then the object is serialized as Dog, not as Animal.
The other side of the line (where the object is supposed to be deserialized) doesn't know about Dogs, it only knows about Animals (i.e. there's only the assembly defining Animal available, not the one defining Dog, so trying to deserialize this object will throw a TypeLoadException).
Regards,
mav
--
Black holes are the places where God divided by 0...
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Well, it appears from your code sample as if you really want to serialize the Dog object. I don't understand why you wouldn't want to do that, since you can Deserialize it and cast it back to animal if that's what you really need. Why in the world would the deserialize code not know about the dog object. It looks from here as if your design needs to be re-engineered.
"Why don't you tie a kerosene-soaked rag around your ankles so the ants won't climb up and eat your candy ass..." - Dale Earnhardt, 1997
-----
"...the staggering layers of obscenity in your statement make it a work of art on so many levels." - Jason Jystad, 10/26/2001
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The simplest explanation for what mav's doing is that animal is owned by a different team and are either unwilling or unable to modify the object to contain additional functionality that is needed in mav's part of the project. For every part of the app except serialization having dog inherit from animal makes a more natural design than having dog have an animal member.
Today's lesson is brought to you by the word "niggardly". Remember kids, don't attribute to racism what can be explained by Scandinavian language roots.
-- Robert Royall
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Well, things tend do become simplified when stripping the context.
I have a system of several client applications and a server that are communicating via remoting. They all have a notion of Animal. Animal has a method public static void ToFile(Animal a, string file) (and the corresponding FromFile()).
For a new client, a Dog class had to be created, but since this class is only used with this client it doesn't make sense to put it into the library defining Animal.
Then the client wanted to serialize the Animal-part of one of the Dog objects using the static Animal.ToFile() method, but the binary formatter threw an exception because Dog wasn't marked as serializable.
The most intuitive method (for me) to solve this problem would be to find a way to tell the BinaryFormatter that what he gets really really is just an Animal, but I don't know how.
Other solutions would be to use aggregation instead of inheritance, but that would require some rewriting of existing code.
Or I could add a copy constuctor to Animal and actally create a new object, but that's not really the idea - I don't want to serialize a copy of a Dog, I only want to serialize the Animal-parts of the Dog...
Regards,
mav
--
Black holes are the places where God divided by 0...
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Objects have to have public, empty constructors to be serialization using the built in methods (Don't quote me) and need to have the Serialization attribute as well as the ISerializable interface for binary serialization.
Base classes, in general, can't be serialized if they can't be instantiated.
Need software developed? Offering C# development all over the United States, ERL GLOBAL, Inc is the only call you will have to make.
Happiness in intelligent people is the rarest thing I know. -- Ernest Hemingway
Most of this sig is for Google, not ego.
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Ennis Ray Lynch, Jr. wrote: Objects have to have public, empty constructors to be serialization using the built in methods
Not true. No constructor is used in deserialization AFAIK.
Ennis Ray Lynch, Jr. wrote: Base classes, in general, can't be serialized if they can't be instantiated.
Huh?
Mark Salsbery
Microsoft MVP - Visual C++
![Java | [Coffee]](https://www.codeproject.com/script/Forums/Images/coffee.gif)
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For standard XML serializaiton the default constructor needs to be public. For binary serializaiton you need to have the serialization constructor defined.
Need software developed? Offering C# development all over the United States, ERL GLOBAL, Inc is the only call you will have to make.
Happiness in intelligent people is the rarest thing I know. -- Ernest Hemingway
Most of this sig is for Google, not ego.
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Ennis Ray Lynch, Jr. wrote: For standard XML serializaiton the default constructor needs to be public
What if there's no default constructor?
Ennis Ray Lynch, Jr. wrote: For binary serializaiton you need to have the serialization constructor defined.
Not true. That's only for ISerializable-derived classes.
ISerializable isn't required for binary serialization.
Mark Salsbery
Microsoft MVP - Visual C++
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I will believe you on the second one, however, a default constructor is defined by default unless you create either a non-default constructor or a default constructor with visibility other than public.
See: http://support.microsoft.com/kb/330592[^]
public class Foo{
}
and
public class Foo{
public Foo(){}
}
Both contain default constructors whereas
public class Foo{
public Foo(int a){}
}
and
public class Foo{
private Foo(){}
}
Do not.
Need software developed? Offering C# development all over the United States, ERL GLOBAL, Inc is the only call you will have to make.
Happiness in intelligent people is the rarest thing I know. -- Ernest Hemingway
Most of this sig is for Google, not ego.
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Ennis Ray Lynch, Jr. wrote: a default constructor is defined by default unless you create either a non-default constructor or a default constructor with visibility other than public.
Got it, thanks
Mark
Mark Salsbery
Microsoft MVP - Visual C++
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Also, the constructor is only called when using XmlSerializer.
No constructor is called with binary/SOAP deserialization.
Cheers,
Mark
Mark Salsbery
Microsoft MVP - Visual C++
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I didn't know that, I just assumed a constructor would be called.
Need software developed? Offering C# development all over the United States, ERL GLOBAL, Inc is the only call you will have to make.
Happiness in intelligent people is the rarest thing I know. -- Ernest Hemingway
Most of this sig is for Google, not ego.
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I was trying to convince myself more than you I think 
I knew I read it somewhere once, and testing confirmed it.
Its obscurely "documented" here[^].
I appreciate the discussion, thanks!
Mark
Mark Salsbery
Microsoft MVP - Visual C++
![Java | [Coffee]](https://codeproject.global.ssl.fastly.net/script/Forums/Images/coffee.gif)
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Thanks for the link, it was quite instructive, although I couldn't achieve useable results so far with a SerializationBinder...
Nevertheless: thanks for taking your time.
Regards,
mav
--
Black holes are the places where God divided by 0...
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dogAsAnimal is still a Dog object, regardless of the "cast".
You can see that in the debugger.
"as" doesn't create a new object of a different type.
Mark
Mark Salsbery
Microsoft MVP - Visual C++
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Well, the debugger shows "Animal {Dog}" as type for dogAsAnimal. a yields "Animal" and d yields "Dog", so I expected dogAsAnimal to be an Animal-type reference to an object that is Dog.
It's the same with a direct cast.
I cannot access the Dog-only properties of dogAsAnimal, but the BinaryFormatter seems to see through the cast and serialize the deepest inheritance.
Regards,
mav
--
Black holes are the places where God divided by 0...
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What if you make the Dog class [Serializable], mark all its members
[NonSerialized], and use a SerializationBinder[^]
for deserialization?
I'm not sure if it will work or not
Mark Salsbery
Microsoft MVP - Visual C++
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Thanks for the suggestion, I'll take a look.
Jeez, I didn't expect it to get so complicated... 
Regards,
mav
--
Black holes are the places where God divided by 0...
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