HOWTO: Downloading Dependent DLLs in IE with .inf File

• Microsoft Internet Explorer (Programming), version 3.0, 3.01, 3.02, 4.0

SUMMARY

It is often necessary to download dependent DLLs along with an ActiveX Control. MFC and VB controls have this requirement.

This article will explain three ways which this can be done.

MORE INFORMATION

There are three ways to include dependent DLLs in the download for a control. The first way is to include the DLL(s) in the CAB file for the control along with the OCX and INF files. The downside of this is that the DLL will be downloaded any time the control is downloaded. In some cases, this is appropriate. The next way is to package the dependent DLL(s) in a separate CAB file and refer to that in the INF file for the control. The third way also packages the DLL in a separate CAB file but the CAB file is referred to in the control’s INF file with a hook. Using a hook allows the download process to execute an INF or EXE file contained in the dependent CAB file.

To add a dependency for an OCX (Simpdll.dll in this example), a section similar to the section for the control is added to the [AddCode] section of the INF file:

   [Add.Code]
   TestDw.ocx=TestDw.ocx
   simpdll.dll=simpdll.dll

   [simpdll.dll]
   FileVersion=1,0,0,1
   file-win32-x86=thiscab

To include the DLL in a separate CAB file, all that is necessary is to change the location from "thiscab" to the URL at which the dependent CAB will be located:

   file-win32-x86=http://example.microsoft.com/simpdll.cab

Multiple DLLs can be added to the INF and CAB files above if necessary.

The third way to package dependent DLLs is to refer to the dependent DLL’s CAB file using a hook. With this technique, an INF or EXE file in the dependent CAB can be executed on download.

The following section from an .inf file controls the dependent DLL download for MFC controls:

   [Add.Code]
   ...
   msvcrt.dll=msvcrt.dll
   mfc42.dll=mfc42.dll
   olepro32.dll=olepro32.dll

   [msvcrt.dll]
   FileVersion=4,20,0,6164
   hook=mfc42installer

   ...

   [mfc42installer]
   file-win32-x86=http://activex.microsoft.com/controls/vc/mfc42.cab
   run=%EXTRACT_DIR%\mfc42.exe

   [yourinstaller]
   file-win32-x86=http://example.microsoft.com/simpdll.cab
   InfFile=your.inf

To illustrate, the following is the .inf file used to install the dependent MFC DLLs. You can modify this to install your own DLLs in the same way that the MFC DLLs are installed.

   ; ========================= Mfc42.inf =========================

   ; This file will control the download of the MFC 4.2 DLLs

   [version]
   ; version signature (same for both NT and Win95) do not remove
   signature="$CHICAGO$"
   AdvancedINF=2.0

   [SourceDisksNames]
   ; This section specifies that all sources are in the "default"
   ; location.
   1="default",,1

   [DefaultInstall]
   ; Default section to process and copy all files under the section
   ; mfcdllsx.files and Register DLLs under the section mfcdllsx.register.
   CopyFiles=mfcdllsx.files
   RegisterOCXs=mfcdllsx.register

   [DestinationDirs]
   ; Destination Directories for CopyFiles Sections.
   ; 11 indicates LDID_SYS - system directory
   mfcdllsx.files=11

   [mfcdllsx.files]
   ; ,,,32 - Suppress version conflict dialog and don't overwrite newer
   ; DLLs
   msvcrt.dll,,,32
   mfc42.dll,,,32
   olepro32.dll,,,32

   [mfcdllsx.register]
   ; msvcrt.dll is not self registering
   %11%\mfc42.dll
   %11%\olepro32.dll

   ; ====================== Mfc42.inf ======================

Beware, however, that running Regsvr32 on the DLL may have undesirable side effects. When DllRegisterServer is called, it makes appropriate registry entries pointing to the DLL location on the machine. For example, typing the following in a DOS prompt, for test purposes, can cause problems:

   copy mfc42.dll C:\Test
   run "D:\msdev\bin\REGSVR32.EXE C:\Test\mfc42.dll"
   delete mfc42.dll

Installing a DLL with a hook and a self extracting EXE is useful for the following reason: If a DLL that needs to be upgraded is already loaded in memory, the download will fail. This is a known problem, which has been fixed in Internet Explorer version 4.0. Internet Explorer 4.0 will suggest a reboot and load the new DLL during the reboot.

REFERENCES

For additional information, please see the following articles in the Microsoft Knowledge Base:

   ARTICLE-ID: Q167158
   TITLE     : How To Package MFC Controls for Use Over the Internet

   ARTICLE-ID: Q167597
   TITLE     : Specifying FileVersion and #Version for Component Download

Keywords          : AXSDKCompDownload kbhowto
Version           : Win:3.0,3.01,3.02,4.0
Platform          : WINDOWS
Issue type        : kbhowto