Internet Information Services (IIS) ISAPI (Internet Server Application Programming Interface) extensions and filters can extend and modify the request-processing capabilities of IIS. ISAPI filters require a long time to be written, offer no native support for session handling, and can be cumbersome to maintain. IIS 6.0 and IIS 7 run ISAPI applications in isolation to enhance server stability. While ISAPI filters can still be used in IIS 7, it is easier for developers to add managed or native modules that integrate into IIS 7’s new modular architecture.

SF_NOTIFY_READ_RAW_DATA not supported on IIS 7

IIS 7 no longer supports the SF_NOTIFY_READ_RAW_DATA notification for ISAPI filters. If you have to use an ISAPI Filter that requires this notification, you must run the filter on IIS 6.0 in IIS 5.0 Isolation Mode (however, notice that this is not a recommended practice). For more information, see the article Information about ISAPI filters that register the SF_NOTIFY_READ_RAW_DATA event in Internet Information Services version 6.0.