I\'m aware of a number of coding standards and guidelines for C# 2 and C# 3 but am looking for some which have been written with C# 4 in mind.
Try the new Edition of Effective C#.
I have found recently this article about code contracts in C# 4.0 which is part of C# in Depth, Second Edition book.
I'm in the process of publishing new coding guidelines for C# 4.0 here.