Returns one of the following values that indicate how the application handled the event.
The filter has handled the HTTP request. The server should disconnect the session.
This filter is not supported.
The next filter in the notification chain should be called.
This filter handled the notification. No other handlers should be called for this particular notification type.
Tells IIS that an error occurred during the processing of the request. The filter should call SetLastError with the nature of the failure, otherwise the client might get an unexpected response. IIS looks at GetLastError and the notification where the error occurred to decide what error to send to the client. For example, if the filter calls SetLastError with a "File not found" error, IIS will return a 404 to the client.
The filter is an opaque stream filter (encrypted/compressed HTTP requests) and the session parameters are being negotiated. This is valid only for raw-read notification. This notification indicates that the full request has not yet been received; the Web server should issue another read and notify the filter with the additional data read.
This function usually serves as the dispatch for an ISAPI filter. Separate functions are often created to serve as handlers for the separate notifications, especially if the handling code is complicated.