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Basics of .NET Framework Serialization 

Serialization is the process of converting an object into a stream of bytes in order to persist it to memory, a database, or a file. Its main purpose is to save the state of an object in order to be able to recreate it when needed. The reverse process is called deserialization.

How Serialization Works

This illustration shows the overall process of serialization.

Serialization Graphic

The object is serialized to a stream, which carries not just the data, but information about the object's type, such as its version, culture, and assembly name. From that stream, it can be stored in a database, a file, or memory.

Uses for Serialization

Serialization allows the developer to save the state of an object and recreate it as needed, providing storage of objects as well as data exchange. Through serialization, a developer can perform actions like sending the object to a remote application by means of a Web Service, passing an object from one domain to another, passing an object through a firewall as an XML string, or maintaining security or user-specific information across applications.

Making an Object Serializable

To serialize an object, you need the object to be serialized, a stream to contain the serialized object, and a Formatter. System.Runtime.Serialization contains the classes necessary for serializing and deserializing objects.

Apply the SerializableAttribute attribute to a type to indicate that instances of this type can be serialized. A SerializationException exception is thrown if you attempt to serialize but the type does not have the SerializableAttribute attribute.

If you do not want a field within your class to be serializable, apply the NonSerializedAttribute attribute. If a field of a serializable type contains a pointer, a handle, or some other data structure that is specific to a particular environment, and the field cannot be meaningfully reconstituted in a different environment, then you may want to make it nonserializable.

If a serialized class contains references to objects of other classes that are marked SerializableAttribute, those objects will also be serialized.

Binary and XML Serialization

Either binary or XML serialization can be used. In binary serialization, all members, even those that are read-only, are serialized, and performance is enhanced. XML serialization provides more readable code, as well as greater flexibility of object sharing and usage for interoperability purposes.

Binary Serialization

Binary serialization uses binary encoding to produce compact serialization for uses such as storage or socket-based network streams. It is not suitable for passing data through a firewall but provides better performance when storing data.

XML Serialization

XML serialization serializes the public fields and properties of an object, or the parameters and return values of methods, into an XML stream that conforms to a specific XML Schema definition language (XSD) document. XML serialization results in strongly typed classes with public properties and fields that are converted to XML. System.Xml.Serialization contains the classes necessary for serializing and deserializing XML.

You can apply attributes to classes and class members in order to control the way the XmlSerializer serializes or deserializes an instance of the class. For more information, see Controlling XML Serialization Using Attributes and Attributes That Control XML Serialization.

This table lists tasks associated with XML serialization:

To See

Serialize an object

How to: Serialize an Object

Deserialize an object

How to: Deserialize an Object

Generate classes and XML Schema documentation

How to: Use the XML Schema Definition Tool to Generate Classes and XML Schema Documents

Qualify XML element and XML attribute names

How to: Qualify XML Element and XML Attribute Names

Specify an alternate element name for an XML Stream

How to: Specify an Alternate Element Name for an XML Stream

Control serialization of derived classes

How To: Control Serialization of Derived Classes

SOAP Serialization

XML serialization can also be used to serialize objects into XML streams that conform to the SOAP specification. SOAP is a protocol based on XML, designed specifically to transport procedure calls using XML. As with regular XML serialization, attributes can be used to control the literal-style SOAP messages generated by an XML Web service. For more information, see XML Serialization with XML Web Services and Attributes That Control Encoded SOAP Serialization.

This table lists tasks associated with SOAP-encoded XML serialization:

To See

Serialize an object as a SOAP-encoded XML stream

How to: Serialize an Object as a SOAP-Encoded XML Stream

Override SOAP-encoded XML serialization

How to: Override Encoded SOAP XML Serialization

Basic and Custom Serialization

Serialization can be performed in two ways, basic and custom. Basic serialization uses the .NET Framework to automatically serialize the object.

Basic Serialization

The only requirement in basic serialization is that the object have the SerializableAttribute attribute applied. The NonSerializedAttribute can be used to keep specific fields from being serialized.

When you use basic serialization, the versioning of objects may create problems, in which case custom serialization may be preferable. Basic serialization is the easiest way to perform serialization, but it does not provide much control over the process.

Custom Serialization

In custom serialization, you can specify exactly which objects will be serialized and how it will be done. The class must be marked SerializableAttribute and implement the ISerializable interface.

If you want your object to be deserialized in a custom manner as well, you must use a custom constructor.

Designer Serialization

Designer serialization is a special form of serialization that involves the kind of object persistence usually associated with development tools. Designer serialization is the process of converting an object graph into a source file that can later be used to recover the object graph. A source file can contain code, markup, or even SQL table information. For more information, see Designer Serialization Overview.

See Also

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