I came across an issue that makes me think there is bug in the 3.0 framework. When I try to use extension methods I get the following error:
Missing compile
in VS, click Project (next to File,Edit,View), select Properties
then in Application tab (you'll notice you're already in 3.5), select the Target Framework to 2.0, then compile (it will error). then put it back again to 3.5, then compile again, the error will disappear
i think it is just a small glitch in Visual Studio, just fool the IDE :-)