IPdxReader ReadUnreadFields Method Pivotal GemFire .NET Client Documentation
To preserve unread data, which get added in new version of type.

Namespace: GemStone.GemFire.Cache.Generic
Assembly: GemStone.GemFire.Cache (in GemStone.GemFire.Cache.dll) Version: 8.0.0.0
Syntax

IPdxUnreadFields ReadUnreadFields()
See Also