Type or namespace could not be found - missing directive /assembly reference?

I am trying an example from a book and I am getting errors.  The main error I am getting is 

Error2 The type or namespace name 'Entitykey' could not be found (are you missing a using directive or an assembly reference?)C:\MyCode\InventoryEDMConsoleApp\InventoryEDMConsoleApp\Program.cs6017 InventoryEDMConsoleApp

I have copied the example identically but it throws up a number of errors about missing assembly or reference.  The example is an console application  where i create a ADO.NET entity data model and follow through the Wizard.  Its a pretty straightforward operation and everything is done before I start editing the code so I can't figure out why it would be throwing up missing a using directive / ssembly reference errors ?

Any ideas ?