Just add the EntityFramework as "Code First from database" and not as "EF Designer from database". This resolved my problem, but it has a dark side, if you change your database you have to remove all the classes and add it again, or just edit the classes, I use the last when I change properties of the columns, like "Allows null" or the size of a string. But if you add columns I recomend remove and add again the classes.