datacontext not found in vs2010 sp1

I am starting to learn some linq and there is a place where I need to use datacontent, but it seems that the IntelliSense can't found any datacontent. Am I missing something? I am running VS2010 SP1. Scree开发者_C百科nshot attached. Thanks in advance for your help.

DataContext is defined in the System.Data.Linq namespace, which you don't have in your using statements. Make sure the System.Data.Linq assembly is referenced, then add that using statement.