Serialization refers to the process of transforming data from an object instance in memory into a structured representation of that data in a stream. Serialization allows you to preserve the state of an application’s objects, whether to simply save the data you’re working with or to transmit the data to another application. By using the framework to serialize an object to a stream, you can avoid much of the tedium of hand-coding the logic of reading each field from the object and writing its data to the stream. Instead, the serialization class knows how to do this translation with minimal intervention from the programmer.

The process of reading a stream of data into a new object instance in memory is deserialization, which is the opposite of serialization. Although you would hope that no data would ever be lost in the serialization-deserialization process, the reality is that different formats support different datatypes, and they do not always map well to each other. .NET takes two different approaches to serialization, runtime serialization and XML serialization. Each has its advantages, and I’ll compare them later.

In runtime serialization, the .NET framework uses a formatter class to create a serialized version of an object, using information available about the object from reflection. Reflection is the mechanism by which objects in memory can be interrogated at runtime for information about their fields, properties, methods, and attributes. Different formatters do the actual work of serialization, based on hints the object provides through reflection.

In XML serialization, the structured representation is defined via XML syntax. I introduced you to a simple form of serialization in Chapter 8, wherein the XmlSerializer class was used to control the transformation specified by an XML Schema document.

XML Schema is one way to specify the serialization format, and I’ll talk about .NET’s XML serialization functionality in a moment. But first, I’ll introduce SOAP.