input: [Category] Data Contracts [Description] While the default behavior of a data contract type is to simply ignore extraneous unexpected members, you can instruct it to still store and pass it along to and from the service by implementing IExtensibleDataObject. This enables a round-trip scenario, where a new client is calling an old service with the new data contract, and the service can even pass the data contract unaffected to another service or client, as shown in the download. [Last Updated] 9/7/2006 [Title] 
output: Data Extensions and Round Trip