I demo’d code contracts in my session at DevConnections. When I did a Camtasia video of the talk I found that they were not working. This led to a frustrating few hours, as I really wanted to complete the recording. Let me explain what I think happened in hopes of saving you some time. Note that this may be entirely different at VS 2010 RTM.
First, the reason they were not working was because runtime checking was turned off. The normal way to turn runtime checking on is through a tab called Code Contracts which appears on the Project Properties dialog. But alas, I had no such tab.
There is a download for code contracts which looks like this on the code contracts page.
Perhaps you would have thought this was intended for VS 2010 Beta 2, but I did not. I also thought I had already installed this because I’ve previously played with contracts in VS 2008, but apparently this didn’t get reinstalled after a machine rebuild.
At Julie Lerman’s suggestion, I reinstalled the Code Contract development tools and the tab appeared. This allowed me to turn runtime checking back on and voila see the failure.
Code contracts are very cool and I hope they will be implemented a bit more cleanly in the final release of VS 2010.