Summary

Symptoms

A deferred execution custom action that either accesses or sets a property is not working.

Cause

This is happening because custom actions have limited access to properties during the Execution sequence of the installation. There are two sequences used by a typical installation program: the User Interface sequence and the Execute sequence. The User Interface sequence displays dialog boxes and queries the target system, but does not make any system changes. The Execute sequence performs system changes, but does not display a user interface. The Execution sequence is when deferred custom actions are executed.

During installation, the Execute sequence runs in two stages, immediate mode and deferred mode. Immediate mode walks through the actions in the Execute sequence, generating an internal, hidden installation script; this script contains, for example, instructions for what files, registry data, shortcuts, and so forth, to install. Immediate mode does not touch the target system. Note that the User Interface sequence runs only in immediate mode.

The second stage of the Execute sequence, deferred mode, carries out the system changes described by this internal installation script. Strictly speaking, deferred mode is performed only for actions between the built-in actions InstallInitialize and InstallFinalize. During deferred execution, MSI property values are fixed and cannot be changed. Moreover, the values of only a handful of MSI properties can explicitly be read during deferred execution.

The properties that are accessible to the deferred custom actions are ProductCode, UserSID, and CustomActionData. Deferred custom actions cannot set any properties.

Resolution

Setting properties

Your deferred custom action can get properties other than ProductCode and UserSID by using the CustomActionData property. If you set a property that has the same name as your deferred custom action before script execution starts, the value of that property will be available to your deferred custom action in the CustomActionData property. You can do this by creating a custom action that sets a property, such as this one:

You can create this using the custom action wizard. Select "Set a property" for type and make [INSTALLDIR] the target. Accept the default choices for the rest of the options. Insert this custom action into the Execute sequence after LaunchConditions. When you run the installation, this immediate execution custom action will set the property DeferredCustomActionName to the value of INSTALLDIR. When script execution begins, the value of DeferredCustomActionName will be available to the custom action named DeferredCustomActionName in the property CustomActionData.

Getting multiple properties

If your deferred custom action needs to access to more than one property, you will need to pack all of these properties into CustomActionData and then make your deferred custom action "unpack" them after it gets CustomActionData. Here is a version of the property setting custom action above, modified to handle multiple properties.

Dim PropArray
PropArray = Split(Session.Property("CustomActionData"), ";") 
INSTALLDIR = PropArray(0)
SetupType = PropArray(1)
OTHERPROP = PropArray(2)
'Now do stuff with these variables...

Additional Information

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