The minor upgrade

Although a minor upgrade, like a major upgrade, can be distributed as a full MSI, in this chapter we'll focus on the more efficient methods of distributing it as a patch file (.msp). In this case, a minor upgrade doesn't uninstall the previous version. It only replaces some of the existing files or adds new ones. I'll show you two ways to make a patch, the first using .wixpdb files and the second using .wixout files.

Before we get to that, let's discuss the WiX source file that defines your patch. A .wixmsp defines the characteristics of your patch, setting fields such as Description and Comments that will appear in the patch file's properties. This file also sets up the sequencing of all of the patches for a particular product so that, say, patch 1.0.2.0 will be applied after 1.0.1.0. In this way, even if a user installs a patch out of order, it won't overwrite a newer patch that's already been applied. This file also defines the CAB files to embed in the patch and which...