The RTM version of Entity Framework 4.1 actually includes extension methods in the
EntityFramework.dll file, for eager loading with lambda through the
Include function. Just include the DLL in your project and you should be able to write code like:
var princesses1 = context.Princesses.Include(p => p.Unicorns).ToList();
Remember to add an Import/Using statement to include the System.Data.Entity namespace. Otherwise the compiler cannot find the extension methods. E.g:
See this ADO.NET team blog article for more information.