IMsmMerge::OpenModule method (mergemod.h)

The OpenModule method opens a Windows Installer merge module in read-only mode. A module must be opened before it can be merged with an installation database. For more information, see the OpenModule method of the Merge object.

IMsmMerge2::OpenModule    Mergemod.dll version 2.0 and later.

IMsmMerge::OpenModule      All Mergemod.dll versions.


HRESULT OpenModule(
  [in] const BSTR  Path,
  [in] const short Language


[in] Path

Fully qualified file name that points to a merge module. A LPCWSTR can be used in place of a BSTR.

[in] Language

A language identifier (LANGID).

Return value

The OpenModule function returns the following values.

Value Meaning
The file specified is a Windows Installer database, but is not a merge module (missing ModuleSignature table).
The language is not supported by the module.
The language is supported by the module, but there was an error applying the transform.
The file could not be opened as a Windows Installer database.
There is already a module open. Closes the current module first.
The function succeeded.


This function opens the merge module in read-only mode (MSIDBOPEN_READONLY), and excludes other programs from writing to the merge module until the CloseModule function is called. A merge module must be opened before it can be merged.

The installer attempts to open the module in the language specified by Language or in any more general language. For example, if 1033 is specified by the Language value, a module with a default language of 1033, 9, or 0 is opened in its default language. A Language value of 9 opens modules with a default language of 9 or 0. If the default language of the module does not meet the specified requirements, an attempt is made to transform the module into the requested language. If that fails, the installer attempts to transform the module into increasingly general languages, all the way to language neutral. If none of the transforms succeed, the module fails to open. In this case, an error is added to the error list of type msmErrorLanguageUnsupported and the function returns ERROR_INSTALL_LANGUAGE_UNSUPPORTED as HRESULT.

If there is an error transforming the module to the desired language, an error is created of type msmErrorLanguageFailed and the function returns ERROR_INSTALL_TRANSFORM_FAILURE as HRESULT.

For more information, see the Type property of the Error object.

Opening a merge module clears any errors that have not already been retrieved.


Minimum supported client Mergemod.dll 1.0 or later
Target Platform Windows
Header mergemod.h
DLL Mergemod.dll

See also

Merge Module Automation