Q:

Why can't I insert record with foreign key in a single server request?

I'm tryring to do a simple insert with foreign key, but it seems that I need to use db.SaveChanges() for every record insert. How can I manage to use only one db.SaveChanges() at the end of this program?
public static void Test()
{
    using (var entities = new DBEntities())
    {
        var sale =
            new SalesFeed
            {
                SaleName = "Stuff...",
            };
        entities.AddToSalesFeedSet(sale);

        var phone =
            new CustomerPhone
            {
                CreationDate = DateTime.UtcNow,
                sales_feeds = sale
            };
        entities.AddToCustomerPhoneSet(phone);

        entities.SaveChanges();
    }
}

After running the above code I get this exception:
System.Data.UpdateException: An error occurred while updating the entries. See the InnerException for details. The specified value is not an instance of a valid constant type
Parameter name: value.
EDIT: Changed example code and added returned exception.

A:

Apperantly using UNSIGNED BIGINT causes this problem. When I switched to SIGNED BIGINT everything worked as it supposed to.

