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Entity Framework: Shouldn't attaching the following entity throw an exception?
Employee employee = context.Employees.First();
        Address address = context.Addresses.First();
        employee.Addresses.Attach(address);

Employee employee = context.Employees.First();
        Address address = context.Addresses.First();
        employee.Addresses.Attach(address); // System.InvalidOperationException: A
                                            // referential integrity constraint
                                            // violation occurred

var existingPerson = ctx.Persons.SingleOrDefault(p => p.Name = "Joe Bloggs" };
var myAddress = ctx.Addresses.First(a => a.PersonID != existingPerson.PersonID);
existingPerson.Addresses.Attach(myAddress);
// OR:
myAddress.PersonReference.Attach(existingPerson)
ctx.SaveChanges();

var existingPerson = ctx.Persons.SingleOrDefault(p => p.Name = "Joe Bloggs" };
var myAddress = ctx.Addresses.First(a => a.PersonID == existingPerson.PersonID);
existingPerson.Addresses.Attach(myAddress);
// OR:
myAddress.PersonReference.Attach(existingPerson)
ctx.SaveChanges();