Sequences

You can think of a sequence as a timeline that contains all of the high-level elements of your setup. These sequences are exposed in the Sequences view. Each Windows Installer sequence is described below:

• Installation sequence   the sequence that executes when the setup runs in the default installation mode, such as when you double-click on an .msi file
• Advertisement sequence   the sequence that executes when you launch the setup with the /j command-line option
• Administration sequence   the sequence that executes when you launch the setup with the /a command-line option

Then, each main sequence can have both a User Interface and an Execute sequence. In broadest terms, the User Interface sequence contains the actions and dialogs necessary for the Setup wizard, and the Execute sequence lists the actions that occur as the target system is modified by the setup.

You can edit any of the sequences to change the order of the actions and dialogs, insert new actions and dialogs, and remove existing items.

Every element in a sequence can have a condition associated with it. The action is executed only if the condition evaluates to true. For example, to have an action run only if the product is being installed for the first time, place the following statement in the action's Condition property in the Sequences view:

    Not Installed

Installation vs. Uninstallation

The concept of uninstallation is very different in Windows Installer from traditional setups. For one thing, no separate program is required. And, you don't have to do any extra work to log events.

Windows Installer has its own mechanisms for keeping track of which components are installed and which actions executed. After a product has been installed, each subsequent time the setup runs, the installer detects that it is in “maintenance mode.” Then, you can instruct the installer to reinstall, repair, or remove the application.

Removing is similar to uninstalling a product. You can trigger a complete uninstallation in any of the following ways:

• Run MsiExec.exe with the /x command-line option
• Right-click on an .msi file in Windows Explorer and select Uninstall
• Set the Windows Installer property REMOVE to All

The default end-user dialog takes care of setting the maintenance mode options for you. The MaintenanceType dialog contains logic that reinstalls, repairs, or removes the product based on the user's selections. Clicking the Remove or Change button in the Add/Remove Programs applet also launches the setup with the specified maintenance mode setting.

When a product is removed, the installer proceeds through the selected sequences. That is, there are no separate sequences for maintenance mode or uninstallation; you can uninstall an application in the Installation, Advertisement, or Administration sequence. However, different actions may be performed—there are many corresponding installation and removal actions that are available for the Execute sequences. For example, if you look at the default Installation Execute sequence, you'll notice both an InstallFiles and a RemoveFiles action. InstallFiles is executed only when the product is being installed for the first time, reinstalled, or repaired, and RemoveFiles is executed only when it is being wholly or partially removed.