I have a situation where I need to serialize an object but don't want to serialize any of its references. This is because I don't know in advance which dlls the object might be referencing and therefore can't ensure that they are serializable objects. This has arisen from needing to serialise plugins to preserve their state.
Am I right in thinking that this is the case with XML serialization (shallow)? But that this will ignore anything private in the object - which isn't what I want?
Is this somehow possible?
Xml Serialization will only work on things that are publicly accessible. Also, unless you mark a public property / field with the [XmlIgnore] attribute, it will be serialized.
If you're just looking at some method of serialization, then use binary serialization. It will serialize the internal state of the object (all fields, private or otherwise). You can use the [NonSerialized] attribute to ignore specific references if you want.
If you know at the type declaration time which references should not be serialized you can use binary serialization and filter out members with the [NonSerialized] attribute.
Put NonSerialized attribute in case of binary and XmlIgnore attribute in case of xml serialization to reference properties or fields
You do know which properties you can serialize, though, correct? Are these plugins implementing a common interface? If that is the case, you should be able to write a generic serializer that will only serialize the specific properties that you choose.
Here is a basic example that will give you the idea of what you need to do:
Object Serialization using C#
If you are just looking to serialize native types within your class instances, you should just be able to implement ISerializable, though, and decorate the properties that you do not want to be serialized.
You can try something like this:
Type myType = currentObject.GetType();
Then check to see if the object is serializable by using:
myType.IsSerializable; //returns a bool
That should tell you whether or not the object is serializable. If you really need to know whether every single object inside of a class is serializable, such as other nested classes or custom types, then you could probably use reflection to read each object, use the code above, and verify whether or not it is serializable. This, however, might be a more complicated approach, and may not be plausible, especially if you have overhead issues to deal with.
It may be useful for you to separate what you want to persist from how you persist it.
It seems like you want control over how you want to persist data, but obviously, cannot know what it is, because of your plugin model.
One scheme that may make sense to you is to give your plugins some sort of object or interface they can write to and read from when its time to save / load. Its fine to document these constraints.
For example, when persisting, allow your plugins to pass to you:
some arbitrary byte array which they are responsible for serializing / deserializing. Then it is a plugins responsibility to make sure they use objects that are appropriately serializable.
a dictionary of strings
an xml file
others...
Store this information per plugin (in whichever form you want), and loading up again, pass back the same information.
This is simply an approach around the fact that in the end, the plugin knows what it needs to save, and needs to own that piece of information.
Related
I have a class which i am serializing. I annotated it with [Serializable] and i am using binary serializer. Everything works fine.
But later i introduced new properties, which cannot be serialized (lets say they contain a lot of mess about GUI which does not need to be rembered). I can compute these properties based on other properties of class.
I need to do it two times, when I serialize - clean mess and enter stabile state ready for serialization. And deserialization - again compute all needed properties.
I need to react on 'events' instance is being serialized/deserialized.
However I can't find these events because I am not implementing the interface ISerializable or abstract class Aserializable but only class atribute [Serializable].
I do not know when class is being serialized because it is not the concern of this class; it is serialized as a field of another class.
Is there a way I can react on those events?
You can use OnDeserializedAttribute and its related attributes (OnSerializing, OnSerialized, OnDeserializing) to create special methods that are called during the serialization/deserialization process.
Build Custome Serialization by Implementing ISerializable. Use OnSerializingAttribute, to manipulate object before serilazation and OnDeserializingAttribute, to manipulate before deserialization.
Have you considered per chance the [XmlIgnoreAttribute] attribute? It will prevent a property to be serialized. No need to tamper withe the serialization workflow.
My bad, didn't realize you wanted to reload some property on deserialization. So why not serialize these? In an optional subObject, or whatever?
I've got a class which contains a number of resources which are loaded from files. Want to serialize objects of this class to XML but with paths to the resources instead of the actual resources themselves.
Right now I have got around this by creating a number of ResourceSource fields which store the path to the resource and using XMLIgnore on the resources themselves. However, these have to be public which isn't so good.
It would seem that what I really want is to be able to create special property accessors which are only executed by XMLSerialize. Does this feature exist or is there a way I might be able to implement it?
Alternatively, can I set my ResourceSource fields to be accessible only by XMLSerialize?
Have you looked at implementing IXmlSerializable instead? This allows you finer grained control over the serialization process.
There are two reasons to implement this interface. The first is to control how your object is serialized or deserialized by the XmlSerializer. For example, you can chunk data into bytes instead of buffering large data sets, and also avoid the inflation that occurs when the data is encoded using Base64 encoding. To control the serialization, implement the ReadXml and WriteXml methods to control the XmlReader and XmlWriter classes used to read and write the XML.
The second reason is to be able to control the schema. To enable this, you must apply the XmlSchemaProviderAttribute to the serializable type, and specify the name of the static member that returns the schema.
It sounds like your class is being overloaded to have multiple responsibilities, which is almost always a red flag that it's time for some refactoring.
What I would do is have one serializable class that stores the resource paths and another that stores the resources themselves. The constructor for the non-serializable class could take an instance of the serialized class, load the resources from disk, etc.
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?
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.
First off, you don't have to.
It is simply a marker interface that tells the serializer that the class is composed of items that it can serialize (which may or may not be true) and that is can use the default serialization.
The XMLSerializer has the additional requirement to have a zero parameter constructor to the class.
There are other serializers that use contracts for serialization (such as the DataContractSerializer) - they give you more control over serialization than simply marking a class as Serializable. You can also get more control by implementing the ISerializable interface.
It's basically metadata that indicates that a class can be serialized, nothing more.
It is required by a lot of framework serializers, which refuse to deal with types not having this attribute applied to them.
Serialization can create security holes and may be plagued by versioning problems. On top of that, for some classes, the very idea of serialization is outright nonsense.
For details, see the excellent answers to Why Java needs Serializable interface?, especially this one, this one, and this one. They make the case that serialization should be a feature you have to explicitly opt into.
For a counterpoint, the accepted answer to that question makes the case that classes should be serializable by default.
It indicates to the serializer that you want that class to be serialized as you may not want all properties or classes to be serialized.
I see it as a reminder that I will allow the class to be serialized. So you don't implicitly serialize something you shouldn't.
Don't know it that is designers' intention.
BTW, I just love BinaryFormatter and use it as much as I can. It handles pretty much of the stuff automatically (like rebuilding complex object graphs with recurring references spread throughout the graph).
I have an object (User) which is not marked as [Serializable()].
I need to convert the entire object (including child objects) to string.
This is an actual need to convert the object from a third party tool response which is not marked as [Serializable()].
How can i convert an entire C# object to string/xml of the above scenario?
The XmlSerializer does not need the Serializable attribute, but it can only serialize public members.
Best Regards
Oliver Hanappi
Edit: You can create your own adapter class, which implements the IXmlSerializable interface and represents one User object which your adapter gets when constructed.
If JSON satisfies your needs, you can try JsonExSerializer as it does not need any attributes to decorate targeted objects.
You could use reflection to find all of the members that you are interested in e.g. public properties and/or private fields and then construct an xml document as you go.
That way would could keep the code generic and as custom as you like. :)
However, remember that reflection can be a very slow process at runtime. :(
I'm using the DataContractSerializer to serialize an objects properties and fields marked with DataMember attributes to xml.
Now a have another use case for the same class, where I need to serialize other properties and other fields.
Are there a way to add "another DataMemberAttribute" that can be used for my other serialization scenario?
No, basically.
If you want to use the existing DataContractSerializer, you'll have to maintain a second version of the DTO class and convert the data between them.
Options if you are writing your own serialization code:
declare your own [DataMember]-style attribute(s) and interpret them at runtime in your own serialization code
use a "buddy class"
use external metadata (such as a file)
use code-based configuration (i.e. via a DSL)
In reality, I expect the first will be the simplest choice.
In a similar scenario in the past, we've taken an Object Oriented approach, and created a new class that extends from the main class.
To help you achieve inhertience with the DataContractSerializer, check out KnownTypeAttribute
In one of your comments to your question,
If the same class is implementing multiple interfaces, certain data elements may be relevant to only one of the interfaces.
If that is the case in your scenario, then perhaps your Data Service Contracts should be exposing just the Interfaces, and not the Class?
For example, if you have a class like:
[DataContract]
public class DataObject : IRed, IBlue
then rather than have your operation contract expose DataObject, you have two operation contracts one for IRed and one for IBlue.
This eliminates the need for custom serialization code.
There is a way to do it, but it's an ugly hack.
The DataContractSerializer can serialize objects that implement the IXmlSerializable interface. You could implement the interface and create your own ReadXml(XmlReader reader) and WriteXml(XmlWriter writer) methods that could serialize the object in different ways.
Note that you'd have to have a flag embedded within the class itself to determine which way to serialize the object. (There's no way to tell the DataContractSerializer which mode to use, so the flag has to be contained in the object itself.)
A second version of the DTO class, as #Marc suggests, would be much cleaner.