An extension may not have a session controller, in which case this property will be null. If a session controller was registered during initialization of the extension Controller then it will always be available (because if it can't be created the entire extension will be skipped)
Requirements
Target Platforms: Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2