Serializing and Encoding in WCF

Whereas serialization defines how .NET objects map to XML Infosets, the encoding defines how the XML Infoset is written out to a stream of bytes.

The serializer is considered part of the service contract because it directly impacts your code. The encoding isn't considered part of the service contract, but rather a configuration detail since it doesn't impact your code—you control the encoding by configuring the endpoint's binding.

The separation of serialization from encoding makes it possible to build your applications on a consistent data model (the XML Infoset) while providing flexibility in representation (the encoding).

Windows Communication Foundation supports three serializers: XmlSerializer, DataContractSerializer, and NetDataContractSerializer. DataContractSerializer is the default.

WCF currently supports the following encodings: text, binary, Message Transmission Optimization Mechanism (MTOM), and your own custom encodings.

From Service Station: Serialization in Windows Communication Foundation by Aaron Skonnard.