Determining Installation Context

An application can call the MsiEnumProducts or MsiEnumProductsEx functions to enumerate products that are installed or advertised on the system. This function can enumerate all the products installed in the per-machine installation context. It can enumerate the products installed in the per-user context for the current user. The application can retrieve information about the context of these products by calling the MsiGetProductInfoEx or MsiGetProductInfo functions.

The Windows Installer can install products to run with elevated (system) privileges for non-administrator users. This requires the permission of an administrator user. A product that is installed with elevated privileges is called "managed." All products installed per-machine are managed. Products installed per-user are only managed if a local system agent performs an advertisement while impersonating a user. This is the method used by software deployment through Group Policy. Per-user applications installed while the AlwaysInstallElevated policies are set are not considered managed. By calling MsiIsProductElevated, an application can check whether a particular product is managed.

The following sample demonstrates how an application determines context by using MsiEnumProducts, MsiGetProductInfo, and MsiIsProductElevated.

#ifndef UNICODE
#define UNICODE
#endif //UNICODE

#ifndef _WIN32_MSI
#define _WIN32_MSI 200
#endif //_WIN32_MSI

#include <stdio.h>
#include <windows.h>
#include <msi.h>
#pragma comment(lib, "msi.lib")

const int cchGUID = 38;

UINT DetermineContextForAllProducts()
{
    WCHAR wszProductCode[cchGUID+1] = {0};
    WCHAR wszAssignmentType[10] = {0};
    DWORD cchAssignmentType = 
            sizeof(wszAssignmentType)/sizeof(wszAssignmentType[0]);
    DWORD dwIndex = 0;

    DWORD cchProductName = MAX_PATH;
    WCHAR* lpProductName = new WCHAR[cchProductName];
    if (!lpProductName)
    {
        return ERROR_OUTOFMEMORY;
    }

    UINT uiStatus = ERROR_SUCCESS;

    // enumerate all visible products
    do
    {
        uiStatus = MsiEnumProducts(dwIndex,
                          wszProductCode);
        if (ERROR_SUCCESS == uiStatus)
        {
            cchAssignmentType = 
                sizeof(wszAssignmentType)/sizeof(wszAssignmentType[0]);
            BOOL fPerMachine = FALSE;
            BOOL fManaged = FALSE;

            // Determine assignment type of product
            // This indicates whether the product
            // instance is per-user or per-machine
            if (ERROR_SUCCESS == 
                MsiGetProductInfo(wszProductCode,INSTALLPROPERTY_ASSIGNMENTTYPE,wszAssignmentType,&cchAssignmentType))
            {
                if (L'1' == wszAssignmentType[0])
                    fPerMachine = TRUE;
            }
            else
            {
                // This halts the enumeration and fails. Alternatively the error
                // could be logged and enumeration continued for the
                // remainder of the products
                uiStatus = ERROR_FUNCTION_FAILED;
                break;
            }

            // determine the "managed" status of the product.
            // If fManaged is TRUE, product is installed managed
            // and runs with elevated privileges.
            // If fManaged is FALSE, product installation operations
            // run as the user.
            if (ERROR_SUCCESS != MsiIsProductElevated(wszProductCode,
                                         &fManaged))
            {
                // This halts the enumeration and fails. Alternatively the error
                // could be logged and enumeration continued for the
                // remainder of the products
                uiStatus = ERROR_FUNCTION_FAILED;
                break;
            }

            // obtain the user friendly name of the product
            UINT uiReturn = MsiGetProductInfo(wszProductCode,INSTALLPROPERTY_PRODUCTNAME,lpProductName,&cchProductName);
            if (ERROR_MORE_DATA == uiReturn)
            {
                // try again, but with a larger product name buffer
                delete [] lpProductName;

                // returned character count does not include
                // terminating NULL
                ++cchProductName;

                lpProductName = new WCHAR[cchProductName];
                if (!lpProductName)
                {
                    uiStatus = ERROR_OUTOFMEMORY;
                    break;
                }

                uiReturn = MsiGetProductInfo(wszProductCode,INSTALLPROPERTY_PRODUCTNAME,lpProductName,&cchProductName);
            }

            if (ERROR_SUCCESS != uiReturn)
            {
                // This halts the enumeration and fails. Alternatively the error
                // could be logged and enumeration continued for the
                // remainder of the products
                uiStatus = ERROR_FUNCTION_FAILED;
                break;
            }

            // output information
            wprintf(L" Product %s:\n", lpProductName);
            wprintf(L"\t%s\n", wszProductCode);
                        wprintf(L"\tInstalled %s %s\n", 
                fPerMachine ? L"per-machine" : L"per-user",
                fManaged ? L"managed" : L"non-managed");
        }
        dwIndex++;
    }
    while (ERROR_SUCCESS == uiStatus);

    if (lpProductName)
    {
        delete [] lpProductName;
        lpProductName = NULL;
    }

    return (ERROR_NO_MORE_ITEMS == uiStatus) ? ERROR_SUCCESS : uiStatus;
}

Related topics

MsiEnumProducts

MsiGetProductInfo

MsiGetProductInfoEx

MsiIsProductElevated

Installing a Package with Elevated Privileges for a Non-Admin

Advertising a Per-User Application To Be Installed with Elevated Privileges

Installation Context