Object Serialization in VB.NET


This application is simple Console application which demonstrate Object Serialization in VB.NET by use of System.Runtime.Serialization namespace.

Technologies Used

VB.NET, IO and Serialization Console application in VB.NET.

What is Object Serialization ?

Serialization is the process of converting a graph of objects, into a linear sequence of bytes. That sequence of bytes can be sent elsewhere (for example, to a remote computer) and Deserialized, thereby making a clone in that remote memory of the original graph of objects. The process of serialization is very easy with .NET and its open too. Every VB 6 programmer have used this feature of Serialization knowingly or unknowingly. When any class in ActiveX dll or ActiveX exe is created , there are five property of class that can be set , the last property known as Persistable is what serialization in VB6. As VB6 does this without the user knowledge most of the developer never bothered to know what and how it is done. In VB.NET with common object library, every language supporting .NET architecture known and can use Serialization Feature with the help of RunTime.Serialization Namespace. 

When we do serialization in .NET, the runtime metadata 'knows' all there is to know about each object's layout in memory, its field and property definitions, this makes serialization of objects automatically, without having to write code to serialize each field.

The serialized stream might be encoded using XML, or a compact binary representation. The format is decided by the the Formatter object that is called. Pluggable formatters allows the developer to serialize objects in with the two supplied formats (binary and SOAP) or can be created by developers.

Serialization can take place with any stream, not just a FileStream (like MemoryStream, NetStream, etc.).

Serialization makes use of several classes, as follows:

  • Formatter Responsible for writing object data in some specified format to the output stream. This class is also responsible for driving the deserialization operation.
  • ObjectIDGenerator ObjectIDGenerator generates IDs for objects. It keeps track of objects already 'seen' so that if you ask for the ID of an object, it knows whether to return its existing ID, or generate (and remember) a new ID.
  • ObjectManager Keeps track of objects as they are being deserialized. In this way, deserialization can query the ObjectManager to know whether a reference to an object, in the serialized stream, refers to an object that has already been deserialized (a backward reference), or to an object that has not yet been deserialized (a forward reference).

Each of these components is 'pluggable' the programmer can provide alternatives.

If a class author wishes to take special action when objects of that class are serialized and deserialized, he can choose to implement the ISerializable interface. This allows full control. For example, the author may define his own, custom Serialization Info, to describe parts of the object, or synthesized fields that capture the object state for serialization. If a class implements ISerializable, that interface will always be called in preference to default serialization. An important note on deserialization is that we return the fields in the same order in which they are returned from Reflection. Reflection makes no guarantee that it will follow metadata ordering.

About the sample

This sample demonstrates the runtime's ability to serialize an object in memory to disk. A singly-linked linked list is created, filled with values, and serialized to a file on disk. The list is then deserialized from the file on disk, restoring it to an object in memory. The elements within the list are then swapped multiple times. Please drop me a line or two regarding the application.

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