C# 3.0 Design Patterns by Judith Bishop
http://patterns.cs.up.ac.za/[
^]
is a good book for C#.
But Head First design patterns
http://shop.oreilly.com/product/9780596007126.do[
^] is really a good book for a conceptual understanding of design patterns and can be followed easily even though the book is in Java.
http://www.dofactory.com/Default.aspx[
^] is good for examples on Design Patterns
The authority on design patterns is of course
http://www.amazon.com/Design-Patterns-Elements-Reusable-Object-Oriented/dp/0201633612[
^] by Erich Gamma, Richard Helm, Ralph Johnson and John Vlissides, but is some what difficult and can be used after getting some idea with the above books.