I want to get the build status in TFS (whether it is succeeded or failed). Which classes and methods can be used for this purpose?
You can run Build Notifications, which is similar to CC Tray in that it will continually give you the status of all builds that you're interested in following. To launch the tool, go to...
All Programs-->Microsoft Visual Studio 2010-->Team Foundation Server Tools-->Build Notifications
Click on the Options button to subscribe to whichever builds are on your server. This will now show up in your system tray with a green check box or red X to indicate the status of the builds you've selected.