With the release of URL-rewrite module for IIS 7.0 and the inclusion of ASP.NET routing into the .NET Framework 3.5 SP1, there have been a lot of questions from ASP.NET developers about how these two features relate to each other and when to use each. The intention of this document is to describe the differences between these two technologies and to provide guidance for Web developers on when to use IIS URL rewriting and when to use ASP.NET routing.
From a high-level point of view, it may seem that these technologies provide very similar functionality–both allow your Web applications to have user-friendly and search-engine-friendly URLs. However, there are fundamental differences between these two technologies that are important to understand in order to make the right choice when deciding what to use for your Web application. In order to help you understand those, we will first explain how IIS URL rewriting and ASP.NET routing work.