I'm still mainly using Visual Studio 2008, but today I was working on a sample project in Visual Studio 2010 to better familiarize myself with the new IDE and get a better grasp on WPF. I have a common library of reusable classes that is my code arsenal, built over the span of 8 years. Visual Studio would not show the Intellisense for my custom library. I tried deleting the “.suo” file with the solution and also adding an import through the project properties to no avail. Then I found out, my project had been setup for the .Net Framework 4 Client Profile and not the full blown .Net Framework 4. The Client Project is a smaller version of the Framework with the most used features (as I understand it). It’s smaller to deploy and in a lot of instances is everything a program needs. My library however, has a reference to System.Web which is not included in the Client Profile. I changed my solution to target the full .Net Framework 4.0 and sure enough, the Intellisense for my library showed back up in the IDE.