Applied XML Programming for Microsoft .NET.pdf - Csbdu.in

Chapter 11: XML SerializationOverviewSerialization is the run-time process that converts an object, or a graph of objects, to alinear sequence of bytes. You can then use the resultant block of memory either forstorage or for transmission over the network on top of a particular protocol. In theMicrosoft .NET Framework, object serialization can have three different output forms:binary, Simple Object Access Protocol (SOAP), and XML. We touched on binaryserialization in Chapter 9 while examining how to work around XML DiffGram code inserialized DataSet and DataTable objects. In this chapter, we'll look briefly at SOAPserialization and then move on to the core topic—XML serialization.Run-time object serialization (for example, binary and SOAP) and XML serialization aresignificantly different technologies with different implementations and, more important,different goals. Nevertheless, both forms of serialization do just one key thing: theysave the contents and the state of living objects out to memory, and from there to anyother storage media. Run-time serialization is governed by .NET Framework formatterobjects. XML serialization takes place under the aegis of the XmlSerializer class.The XML serialization process converts the public interface of an object to a particularXML schema. Such a mechanism is widely used throughout the .NET Framework as away to save the state of an object into a stream or a memory buffer. In Chapter 10, wesaw XML serialization used as a way to persist DiffGram with schema scripts thatdescribe a DataSet object. Web services use the XmlSerializer class to encode objectinstances being returned by methods.The Object Serialization ProcessIn the .NET Framework, object serialization is offered through the classes in theSystem.Runtime.Serialization namespace. These classes provide type fidelity andsupport deserialization. As you probably know, the deserialization process is thereverse of serialization. Deserialization takes in stored information and recreatesobjects from that information.Object serialization in the .NET Framework allows you to store public, protected, andprivate fields and automatically handles circular references. A circular reference occurswhen a child object references a parent object and the parent object also referencesthe child object. Serialization classes in the .NET Framework can detect these circularreferences and resolve them. Serialization can generate output data in multiple formatsby using different made-to-measure formatter modules. The two system-providedformatters are represented by the BinaryFormatter and SoapFormatter classes, whichwrite the object's state in binary format and SOAP format.Classes make themselves serializable through formatters in two ways: they can eithersupport the [Serializable]attribute or implement the ISerializable interface. With the[Serializable] attribute, the class author has nothing else to do, as the serialization takesplace governed by caller applications and the class data is obtained through reflection.The ISerializable interface, on the other hand, enables the class author to exercisecloser control over how the bits of the living object are actually persisted.A formatter is the .NET Framework object that obtains the serialized data from thetarget object. Data is requested either by calling the GetObjectData method on theISerializable interface or through the services of the FormatterServices static class. Inparticular, the GetSerializableMembers method returns all the serializable members fora particular class.In the .NET Framework, formatters are of two types, depending on the nature of theunderlying stream they use. The binary formatter (available through theBinaryFormatter class) saves data to a binary stream. The SOAP formatter (available388