The reason to use ISAPI DLL's is that they are much faster that CGI (*.exe) files. This is particularly true when accessing a database (which is the main reason for writing a web server in the first place).

• Each time a CGI file runs, it needs to connect to the database, perform its task, and disconnect from the database.
• The ISAPI DLL connects to the database the first time it is run. On subsequent calls, that task does not need to be repeated, thus it is much faster.

• Reboot the computer - a bit drastic, and very slow, but when you don't know any other way, it works.
• Under Control Panel / Internet Information Server there is a menu option to restart the server.
• Run a program from the command line.
• Kill dllhost.exe

There are also commands to shut down groups of dll's. (Apparently, this capability was added with IIS 4.)

About Applications

IIS allows you to manage the server as a "group of applications". The server root is always an application. You can add as many as you like. In general, IIS runs as a process and all the applications run in the "pooled" process. For test purposes (as well as for other reasons), you can run an application in its own (isolated) process - for performance reasons, there should be a maximum of 10 isolated applications (processes).

From a test point of view, the main benefit of running your site in an isolated process is that you can shut it down without affecting the other sites running under IIS. This means that to replace an active dll, it is not necessary to restart IIS, instead you just restart the process.

The icon will change to an open box.

(This can also be accomplished via the command line.)

Once any dll in this application is loaded, the Unload button will allow you to stop the execution of all the related dll's so that you can write new versions over the old. (To enable the Unload button, you must reopen the Properties dialog box.)

Reference: IIS 5.1 Documentation - About Applications

  cscript.exe C:\Inetpub\AdminScripts\adsutil.vbs APPUNLOAD /w3svc/1/root/fullPath

This works
  cscript.exe C:\Inetpub\AdminScripts\adsutil.vbs APPUNLOAD /w3svc/1/root

This works
  cscript.exe C:\Inetpub\AdminScripts\adsutil.vbs APPUNLOAD /w3svc/1/root/rlc/nist

These fail
  cscript.exe C:\Inetpub\AdminScripts\adsutil.vbs APPUNLOAD /rlc/nist
  cscript.exe C:\Inetpub\AdminScripts\adsutil.vbs APPUNLOAD /w3svc/1/rlc/nist

with the following error
  Error trying to get the path of the application:

If the path on the vbs file is omitted, then it defaults to

C:\Documents and Settings\userName

It appears that there are 2 VisualBasic Script interpreters

• cscript - for console apps
• wscript - for windows apps

C:\WINDOWS\system32\cscript.exe

Kill (or taskkill or pskill) is much faster than iisreset, but there is the problem of knowing exactly what to kill. For instance killing dllhost.exe produces errors that require you to manually restart IIS after every 6 compiles.

C:\Inetpub\AdminScripts

In a nutshell, this unloads all dlls in a directory

IIsObject = GetObject("IIS://localhost/path")
IIsObject.AppUnload

VAR ogj : IADs;
hr := ADsGetObject('IIS://localhost/xyz', IID_IADsContainer, obj);
obj.

Remember, I started with PWS and older versions of IIS that do not support iisreset.

Basically, the web server (IIS in my case) opens the *.dll file and never closes it. Microsoft does not provide any mechanism for a dll to close itself - it must be closed by the program that opened it. Microsoft also does not provide a way for IIS to close individual *.dll's. As a result, you must shut down and restart IIS before your changes will take effect. (This is why I originally suggested developing your application as a CGI file and testing this first before you use it as a dll.)

The other problem is that the Delphi IDE debugger can not be used unless Delphi runs the code. Thus, when IIS runs your code, you will need to use other methods to debug it.

Dataweb provides Free ISAPI Tools that

• Allow you to unload a dll
• Allow you to distribute an ISAPI dll as an application.

Additionally, the switch applies to the entire site, not just the selected directory.

In XP, the switch is available via,

Control Panel / Administrative Tools / Internet Information Services

• Navigate to the root virtual directory (Default Web Site on my system)
• Right click and select properties
• Select the Home Directory tab
• Click the Configuration... button
• Uncheck Cache ISAPI applications

• Select
  Control Panel / Administrative Tools / Internet Services Manager
• Right click the computer name (in either the left or right pane)
• Select Restart IIS...

• Show the Task Manager (list of programs currently running). Typically, you can use Alt-Ctrl-Del to do this. In windows XP, IIS is on the Services tab.
• Shut down dllhost.exe - there are 2 of them.
• In your browser (this can be on any machine on your network), refresh any page that gets data via your dll. Normally, I get the following error the first time that F5 is pressed, and the new data the second time. (Currently, F5 causes both IE and Netscape to refresh the current page.)

  The remote procedure call failed and did not execute.
  

@echo off

: Kill_ISAPI_dlls.bat
: 10-13-03 by Robert Clemenzi

: This program terminates all currently loaded ISAPI dll's
: It is used for debug 

echo taskkill.exe /f /im dllhost.exe
taskkill.exe /f /im dllhost.exe

C:\INETPUB\WWWROOT\RLC>Kill_ISAPI_dlls.bat
taskkill.exe /f /im dllhost.exe
SUCCESS: The process "dllhost.exe" with PID 2632 has been terminated.
SUCCESS: The process "dllhost.exe" with PID 3552 has been terminated.

taskkill.exe /f /im dllhost.exe

How it works - This Delphi program checks a sub-directory every 5 seconds. When a file is found, it shuts down the server and moves the file(s) to the main directory.

With this program, dll's are just as easy to test as CGI files.

This program does not work with Windows 2000 because taskkill.exe is not available.

Update: This program crashes IIS after changing dll's 5 or 6 times - apparently, there is a limit to how many "errors" IIS will log before it just quits.

A new program using IISRestart.exe is under development.

URL: http:// cpcug.org / user / clemenzi / technical / Databases / Testing_w_IIS.html