Citrix Software Development Kit Limitation when Using the Logoff Method doc

Problem

When the server farm load exceeds 300 users and using the logoff method from the MetaFrameSession Object, users are not prompted to save their work.

Cause

This is by design. No other calls are currently available to allow users to respond.
Workaround
Call the SendMessage to the session first and then call Logoff upon a successful return from SendMessage.