exist a simple and good open source .net CRM?

Hello, I like to learn something about CRM, I see that sourceforge have good ones (splendidCRM is one of that), I like to learn from it, because that, I ask if exist a simple open source CRM developed on .NET (c# or VB.net) to learn from it (web if posible)

thanks for your comments (sorry if I not write good in english, I speak in spanish)

Fabian.