Support for Microsoft Rights Management SDK 3.0 will end on 4/15/2015. All of the functionality in the RMS SDK 3.0 is in the RMS SDK 4.x so, instead use the Microsoft Rights Management SDK 4.x.
The developer documentation for Microsoft Rights Management SDK 3.0 has been relocated to a downloadable CHM file at the RMS Connect site. If you do not already have access to the RMS Connect site, follow these instructions.
public enum GetEncryptedContentSize
The GetEncryptedContentSize enumeration has these members.