I just installed Visual Studio 2010, now how do I get Code Contracts?

Me too!!

Interesting. The capitalization on "Code Contracts" (as opposed to "code contracts") suggests to me that it's a proper noun, and your interpretation didn't occur to me until I read the comments. Since you've been upvoted many times, a lot of people seem to agree with you.

Is English your native language? This seems to be the sort of thing that non-native speakers might miss, but I don't really know.

It looks like a fairly powerful static analysis framework, well beyond what the C# type system can prove. Not sure what exactly it can do, but the static checker dialog box allows you to enable:

  Implicit Non-Null Obligations
  Implicit Arithmetic Obligations
  Implicit Array Bounds Obligations
  Redundant Assumptions

If it can do a good job of checking these statically, I'm impressed!

The big advantage to code contracts is that they prevent null reference exceptions at compile time. Catching potential problems at compile time via static checking is preferable than throwing an exception at runtime. Your code is more resilient to bad data.

Having a formal checking mechanisms like code contracts also helps tools like Pex generate better sets of test inputs for automated unit testing.

Or at least comparable to what the Cobra language has for contract support: http://cobra-language.com/docs/quality/