Sprint 5: Adding the WiX extension namespace to our code

As we've mentioned, the WiX code that you get from HeatWave and that you write yourself is all in XML. And, among other aspects of XML, is the concept of namespaces. Here's a repeat of something we noted way back during Sprint 1:

Note that XML namespaces are uniform resource identifiers (URIs) look like uniform resource locators (URLs) but are not, in actual fact, URLs. WiX uses several namespaces, all of which start with http://wixtoolset.org/schemas/. However, the namespace names aren't valid URLs. You might expect the WiX schema documentation to live at the URLs matching the namespace URIs, but it lives at https://wixtoolset.org/docs/schema/ instead.

The namespace that WiX uses for the "core" language is http://wixtoolset.org/schemas/v4/wxs. WiX requires extensions to have their own, unique namespace when they add XML language elements. The namespace URI for WixToolset.Util.wixext is http://wixtoolset.org/schemas/v4/wxs/util.

So, to use an element from WixToolset.Util.wixext, we need to add http://wixtoolset.org/schemas/v4/wxs/util to the namespaces that are supported in the .wxs file. The easiest way to do that is to declare the namespace in the root Wix element:

<Wix xmlns="http://wixtoolset.org/schemas/v4/wxs"
     xmlns:util="http://wixtoolset.org/schemas/v4/wxs/util">

The namespace declaration breaks down into three parts:

• xmlns: "I am an XML n ame s pace."
• util: This is the prefix I will use for elements in this namespace.
• http://wixtoolset.org/schemas/v4/wxs/util: This is the namespace URI that is too long and annoying to type every time, so I will use the prefix as an abbreviation instead.

We're adding this functionality to the package itself, so modify the Wix element in Package.wxs.