Use the MessageBodyMemberAttribute attribute to specify that a data member is serialized into the SOAP body and to control some serialization items.
The Order property is used to specify the order of body parts in cases where the default alphabetical order is not appropriate.
The other properties are inherited from the base class, System.ServiceModel..::.MessageContractMemberAttribute.
For more information about controlling the serialization of the contents of a SOAP body without modifying the default SOAP envelope itself, see System.Runtime.Serialization..::.DataContractAttribute, Specifying Data Transfer in Service Contracts, and Data Contracts Overview.
For more information, see Using Message Contracts.