I have created a bootstrpper using the dotNetInstaller tool. The created bootstrapper internally has these installers:
- .NET Framework 4.0
- SQL Server Express
Now through WiX, what are the steps that I need to follow to invoke the above Bootstrapper from WiX?
You should not invoke a bootstrapper from WiX - that has no sense. The idea behind the bootstrapper is to "bootstrap" the prerequisites of the installation (.NET and SQL Express in your case) and the main installation package. The main package you generate with WiX should be launched from inside the bootstrapper when the prerequisites are checked and optionally installed.
See this article for better understanding how to start with bootstrapper authoring with WiX.
If you are using WiX to create installers, I would suggest using WiX to create your bootstrapper as well.
http://wix.sourceforge.net/manual-wix3/authoring_bundle_intro.htm
You can only invoke packages from using bootstrapper, you can't invoke it from WiX. By the use of dotNetInstaller you can easily invoke one after another. One of the process as @Yan introduced. By the help of prerequisites folder. It is a very efficient and popular process. But what can I suggest for you, invoke link instead of folder. So your installation full package wouldn't not so bulky. Whatever the msi need it can directly download from internet and install it one after another. Follow the link.
http://www.codeproject.com/Articles/5116/dotNetInstaller-Setup-Bootstrapper-for-NET-Applica