EntryEvent OldValue Property Pivotal GemFire .NET Client Documentation
Returns 'null' if there was no value in the cache. If the prior state of the entry was invalid, or non-existent/destroyed, then the old value will be 'null'.

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

public IGFSerializable OldValue { get; }
See Also