Condition – Use Shared Properties as variables to conditionally execute this action during an update.

Action description – Descriptive text that can be used to identify this particular action in the Actions list.

Client folder – The folder on the deployed client where the files to be patched exists.

Subdirectories – The directory below the designated client root folder that contains the files.

Base folder: The folder on the build machine that includes the baseline file versions.  This folder should represent the deployed client folder.

Target folder: The folder on the build machine that includes the target files.  As the update is built, files in the target folder are compared with their counterpart in the base folder.  If a different version exists in the base folder, a differential patch is created and added to the update.  If the file doesn’t exist in the base folder, the whole file is added to the update.

The Patch Folder action utilizes the Microsoft Delta Compression API to create a differential patch file between two versions of an assembly during an update build, and then packages the patch file into the update.

As the update is executed, this differential patch is combined with the base file that exists on a deployed client to construct the target file.

Utilizing the Patch Folder action can significantly reduce the size of the resulting update package.  The specific version of the baseline files must be present on the system being updated.

NOTE: The Windows Installer SDK must be present on the system building the update package.  Get it here.  Patch extraction support is available on all Windows versions later than Windows 2000.

See Patch Folder Action for more details