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
A section is then added to the INF file to control the installation of the
DLL:
[simpdll.dll]
FileVersion=1,0,0,1
file-win32-x86=thiscab
This is the first way mentioned to include a DLL dependency in a download.
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:
In this case, Simpdll.cab contains only simpdll.dll.
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
In this case, the MFC DLLs are packaged in a self-extracting .exe file,
which is contained in the .cab file (mfc42.cab). However, tools to make
self-extracting .exe files are not currently available from Microsoft.
Therefore, you will either need to package dependent DLLs with an .inf file
or reference the .inf file in the installation hook:
[yourinstaller]
file-win32-x86=http://example.microsoft.com/simpdll.cab
InfFile=your.inf
Or, you will need to build a self extracting EXE file using third party
tools.
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 ======================
A DLL needs to be listed in the .register section if it exports a
DllRegisterServer function. This can be determined by examining the DLL
with the Visual C compiler's Dumpbin.exe utility. You can also run
Regsvr32 on the DLL, which attempts to register the DLL. Regsvr32 loads
the DLL, verifies that DllRegisterServer is properly exported by calling
GetProcAddress() on the DLLRegisterServer function. If it succeeds, the
function DllRegisterServer is exported and is then called.
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 an MS-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
The next time the system tries to look for Mfc42.dll, it looks up the
registry, finds that the file is mapped to C:\Test\Mfc42.dll, and doesn't
find it there. Running Regsvr32 on a file that is already installed on a
machine does not cause problems.
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.