CHttpFilterContext does not have a base class.
CHttpFilterContext provides the tools that a CHttpFilter object needs to process data that passes through the filter. When the filter receives a request, a CHttpFilter object is created and initialized, and a CHttpFilterContext object is created. As the filter processes requests, it uses CHttpFilterContext member functions to perform tasks.
A CHttpFilterContext object exists separately from a CHttpFilter object in order to allow multi-threading. Only one CHttpFilter object exists in a module, but a filter might be required to process multiple client requests simultaneously.
CHttpFilter will create a CHttpFilterContext for each request to handle these multiple requests. A CHttpFilter uses multiple CHttpFilterContext objects to run in separate threads. This design allows simultaneous, multiple calls to the CHttpFilter object by different client connections.
When an extension DLL (ISA) is called, the member function ServerSupportFunction prompts the server to provide the general ISA information to the client.
If the filter must communicate something — for example, an error — back to the client immediately, call WriteClient.