ISAPI Filters and Extensions are used to extend the Microsoft Internet Information Server (IIS) through the ISAPI programming API. An ISAPI Extension can be used to handle a web request in a custom way, however, unlike an extension, an ISAPI Filter can be used to intercept all or some HTTP request at different levels based on need and change the outcome of the whole process in very efficient ways. ISAPI is a low level API usually mastered by C or C++ (Commonly MFC). However, for those of us who love the ease of drag drop visual development and the powerful yet easy VCL, there is Delphi! TbcISAPIFilter component from bestcode.com is designed to help Delphi developers continue to use their beloved Delphi (or C++ Builder) IDE for ISAPI Filter development and utilize their existing knowledge on familiar libraries.

TbcISAPIFilter component brings visual development to your Delphi and C++ Builder environment by letting you point and click to handle events only. Drop the component on a data module and handle the events you wish. Visually set the filter priority. For a quick example, check out the accompanying IIS Authentication Filter sample DLL source code. We have tested TbcISAPIFilter with Delphi 4, 5, 6, 7, 2006, 2007 and C++ Builder 4, 5, 6, 2006.

The Component comes as source code in single .pas file (for Delphi 2006, 2007 design time packages are also included for your convenience). There is a sample project source code which does custom authentication by looking up a database of valid users. There is also a more complicated example of handling SEND_RAW_DATA notifications. There is also a help file for the ISAPIFilter component.

Features:

Drag Drop on your DataModule and:

Users are given a chance to do some initialization in event handlers: OnBeforeProcessGetFilterVersion OnAfterProcessGetFilterVersion or it is also possible to do initialization in DllMain, or Initialization section of a Delphi Unit.

GetFilterVersion tells IIS which and what kind of notifications it should receive.

GetFilterVersion knows which notifications it should register for by looking at the event handler functions assigned for an event that represents a notification.

GetFilterVersion makes sure that request to receive the related notification message is sent to the IIS.

Users of this component can assign event handlers at runtime in the OnBeforeProcessGetFilterVersion event handler.

After OnBeforeProcessGetFilterVersion, it is too late to assign event handlers for notification messages. But users at any time can still assign OnException, OnDestroy.

If the need arises to handle a notification which was not known when this component was designed, users can supply the OnAfterProcessGetFilterVersion handler and they will be given a last chance to modify the HTTP_FILTER_VERSION structure. Such notifications will be handled by the OnUnknownNotification handler.

Exported HttpFilterProc will call the TbcISAPIFilter.HttpFilterProc for actual handling of the notifications.

This function will call the proper user assigned event handler. Possible event handlers that are called from HttpFilterProc are:

If an event handler function is assigned for an event, GetFilterVersion makes sure that request to receive the related notification message is sent to the IIS.

Other useful event handlers: OnDestroy - called when the Filter Object is about to be freed from memory. OnException - called when there is an error.

There are also following event handlers that are called from GetFilterVersion:

Component comes as Delphi source code. There is a sample IIS Authentication Filter project that uses this component. There is also a help file. Version 2.0 includes fix for the multi-threading bug which appeared under heavy load on dual CPU. It also includes support for new IIS 5.0 notifications.

Help file is available for separate download for quick review[139KB]

Software License for your review.

Purchasing TbcISAPIFilter Component for Delphi

You can pay with credit card and download TbcISAPIFilter immediately from our online store for only $19.95. Full version includes Pascal source code. Upgrades are free for registered users. Site license allows any number of developers use the component at your development site. Site licenses can be purchased here.

For technical questions please contact support@bestcode.com

Tips and Screen Shots

Did you know?
You can use iisreset command on the command line (IIS 5.0+ only) so that you can replace a filter DLL with a recompiled version!

Did you know?
If you are handling OnReadRawData, OnSendRawData event, then you must install your filter dll as a global filter in IIS.

Screen shots:

Here is TbcISAPIFilter Component in action:

Here are the events you can handle:

Here are the properties:

More screen shots available in Delphi Installation Page.

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