Technically, Silverlight and ASP.NET are completely different.

The major differences are listed below:

* Silverlight runs completely on the client, while ASP.NET mainly runs on the server, but also has a few parts running on the client.
* When an event fires, Silverlight handles the event on the client, but in ASP.NET, the browser will make an HTTP POST to the server, and after the server handles the request, it sends a new HTML page to the client.
* A Silverlight application sends rendering commands to the Silverlight rendering engine by either writing XAML or code, and the Silverlight rendering engine will handle the rendering task. On the other hand, ASP.NET doesn’t have a rendering engine. It generates an HTML file on the server, sends it to the client, and allows the browser to parse the HTML file and render the content.
* Silverlight can’t work with a database directly; instead, it consumes data from Web Services, while ASP.NET has strong support for working with databases directly.

The most important thing to note is what runs on the client and what runs on the server, since this will affect almost every part of your system. Silverlight runs on the client, and ASP.NET runs on the server. They can work together and are compatible with each other, but this requires some time and effort.