[This is preliminary documentation and subject to change.]
The installer calls dynamic link libraries by creating a separate thread at user privilege. The installer calls the DLL with the handle to the current session as the only parameter. DLL custom actions return the full set of return values described in Custom Action Return Values.
You can call DLLs through the entry point named in the Target column of the CustomAction table. The entry point name specified in the table must exactly match the entry point exported from the DLL.
The following options can be specified for a DLL custom action as described in Custom Action Types.
The DLL can be:
The custom action author can specify whether the action will be run synchronously or asynchronously. Custom actions can also be scheduled to run during install script processing or during rollback as described in Deferred Execution of Custom Actions.