Here are the links which answers a commonly asked question, where do we go to read about design principles or design patterns.

OO Design http://www.oodesign.com/

.NET Design Patterns http://www.dofactory.com/Patterns/Patterns.aspx

http://martinfowler.com/articles/writingPatterns.html

http://www.martinfowler.com/eaaCatalog/index.html

The SOLID Principles in C#

 MSDN

Exploring the Factory Design Pattern

Exploring the Observer Design Pattern

Implementing Singleton in C#,

Implementing Observer in .NET,

Implementing Model-View-Controller in ASP.NET

Enterprise Solution Patterns Using Microsoft .NET

ASP.NET MVC

http://www.asp.net/mvc/tutorials/getting-started-with-ef-using-mvc/implementing-the-repository-and-unit-of-work-patterns-in-an-asp-net-mvc-application

http://blogs.msdn.com/b/adonet/archive/2009/06/16/using-repository-and-unit-of-work-patterns-with-entity-framework-4-0.aspx

 

 and recent one http://www.microsoft.com/net/nettechnologyguidance