Upgrading a Feature or Application by Patching

[This is preliminary documentation and subject to change.]

Microsoft® Windows® installer can upgrade an existing application by patching. In the traditional form of an upgrade an entire new version of a product is installed over the old version. Patching is essentially an efficient form of an upgrade because only the individual file bits needed to update the application are changed. To the user this means that the same upgrade involves downloading a much smaller upgrade patch, rather than the entire product, and that customizations are preserved through the upgrade.

    To apply an upgrade to a product by patching

1. Specify the full path to the patch package containing the upgrade.

   Since the list delimiter for transforms, sources and patches is a semicolon, this character should not be used in these filenames or paths.

3. Specify the path to the product package to receive the upgrade, or choose to have the patch applied to a group of applicable products specified in the Upgrade table. See previous paragraph.
4. Call the MsiApplyPatch function.

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