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Windows Installer FAQ (the basics)
Custom Actions
Types of Custom Actions
Deferred Custom Actions
Deferred custom actions are the opposite of immediate ones and
must be scheduled between "InstallInitialize" and "InstallFinalize".
They have limited access to state information and properties
and so information needs to be passed to them via the Windows Installer
"CustomActionData" property.
They also can't dynamically update the "executing" msi.
Deferred custom actions are executed as part of a transaction and so
you should generally add
commit and Rollback support for any changes
the custom action is making.
Because this supporting code is hard to get right (its difficult) you should
generally use standard Windows Installer functionality where possible.