Windows Installer Dll - Part 1

Audience: Install Developers, Beginner, Windows Installer (MSI) Knowledge

This is Part 1 of a three part series that demonstrates how to use C++ in a Windows Installer Custom Action.

• Introduction
• Part 1 - Creating a Windows Installer .dll
• Part 2 - Calling the Windows Installer .dll from a setup
• Part 3 - Debugging a Windows Installer .dll

Creating a dll to be called in a custom action is easy. I use Visual Studio 2005 (why? – because that's what the company I work at uses, and I like it). Obviously, there are other compilers out there that will get you the same results but, for our purpose we will demonstrate the VC++ way. You’ll be up and running in minutes.

1 - Start a new project.

• Project Type: MFC DLL
• DLL Type: Regular DLL with MFC statically linked
• Name: CustomActions

I find this the quickest and easiest method, the wizard creates everything you need. You could choose other types (like Win32 project) however, MFC DLL is my preference.

I always recommend static linking for Windows Installer Dlls – Typically the Dll will be streamed from the .msi to the %temp% folder, and called from there. Statically linking helps ensure everything you need is contained in one dll.

2 - Update Project Settigns, and Link to Msi.lib

Open the project properties for CustomActions, and link to Msi.lib

Open stdafx.h, add the following includes.

#include <MsiQuery.h>       //Windows Installer API
#include <Msi.h>

3 - Write your Custom Action(s), Export the Function

Open CustomActions.cpp, and add your code. Each Custom Action requires the following prototype.

/*     MyFunction     **************************************

Args: [in] MSIHANDLE hMsi
       - handle to running install (passed by the Windows Installer)

Desc:     Example
************************************************************/
UINT __stdcall MyFunction(MSIHANDLE hMsi)
{

    return ERROR_SUCCESS;
}


Open CustomActions.def and export the function name.

; CustomActions.def : Declares the module parameters for the DLL.

LIBRARY     "CustomActions"

EXPORTS
    ; Explicit exports can go here
     MyFunction


4 - Build the dll

That’s it the dll is ready to go...

The next step is adding the .dll to your setup project, which is covered in Part 2.

Part 2 >

---