The first step in creating any set of extensions is to create a class that implements WixExtension. This class will be the container for all the extensions you plan on implementing.

Creating a bare-bones WixExtension
1. Create a new C# library (.dll) project named SampleWixExtension
2. Add a reference to wix.dll to your project
3. Add a using statement: using Microsoft.Tools.WindowsInstallerXml;
4. Make your SampleWixExtension class inherit from WixExtension.
 public class SampleWixExtension : WixExtension {}
5. Add the AssemblyDefaultWixExtensionAttribute to your AssemblyInfo.cs.
 [assembly: AssemblyDefaultWixExtension(typeof(SampleWixExtension.SampleWixExtension))]
6. Build
7. Although it wont do anything yet, you can now pass the your SampleWixExtension.dll on the command line to the candle and light with the -ext flag like this: candle Product.wxs -ext SampleWixExtension.dll

The next article in this series will explain how to add a Preprocessor extension to your WixExtension.