I see examples about code-only POCO for en entity framework 4, but I cannot find the classes EntityConfiguration and ContextBuilder and I cannot see which reference I need to add to have them.
Is it part of the .Net Framework 4 or do we have to download something else?
The POCO stuff you're looking for is in a separate download. Current version is at http://www.microsoft.com/downloads/details.aspx?FamilyID=af18e652-9ea7-478b-8b41-8424b94e3f58&displayLang=en
Once you run the installer, you'll need to grab the Microsoft.Data.Entity.CTP.dll file (mine was in the C:\Program Files\Microsoft ADO.NET Entity Framework Feature CTP3\Binaries directory). Make a project reference to the new dll and you should be set!
来源：https://stackoverflow.com/questions/2337057/where-is-entityconfiguration-and-contextbuilder-in-visual-studio-2010