Windows Installer 3.1 final (build 1823) redistributable is now out of beta and is available for download. For anyone using the RC (build 1812) will need to uninstall this version before installing the final redistributable.
Notable New features in Windows Installer 3.1:New MinorUpdateTargetRTM property: Patch files can now target both the original release baseline and the latest service-pack-level baseline that is on the system.
New MsiSetExternalUIRecord API: Packages that use an external user interface can now receive messages as records instead of receiving the messages as strings.
New x64 and Msix64 properties: Packages can now use the x64 and Msix64 properties to indicate x64 processor-based operating system support. Download: Windows Installer 3.1 Redistributable
View: Knowledgebase Article
New MsiNotifySidChange API: You can use this API to upgrade the Windows Installer configuration if the security identifier (SID) of a user changes.
Flyweight patching is now an opt-in behavior: Windows Installer 3.0 introduced new "flyweight patching" functionality. By default, this functionality was enabled for all patches. Windows Installer 3.1 now disables this functionality unless you specifically enable the functionality by setting the OptimizedInstallMode property in the MsiPatchMetaData table.
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