使用实体框架的主键（数据库优先）

Question

我有2张桌子。它们是在MySQL中创建的，然后应用数据库优先方法（这意味着在VS中从MySQL导入数据库时​​，所有主键和导航属性都是由实体框架本身设置的）。这两个表通过主键（Id_Cus）连接（一对多）。第一张表

namespace WcfRestFullService.Model
{
    using System;
    using System.Collections.Generic;

    public partial class customer
    {
        public customer()
        {
            this.dishesrankings = new HashSet<dishesranking>();
            this.orders = new HashSet<order>();
        }

        public int Id_Cus { get; set; }
        public string FirstName_Cus { get; set; }
        public string LastName_Cus { get; set; }
        public int PhoneNum_Cus { get; set; }
        public string Email_Cus { get; set; }


        public virtual ICollection<dishesranking> dishesrankings { get; set; }
        public virtual customerpreference customerpreference { get; set; }
        public virtual ICollection<order> orders { get; set; }
    }
}

第二张桌子

namespace WcfRestFullService.Model
{
    using System;
    using System.Collections.Generic;

    public partial class customerpreference
    {
        public int Id_Cus { get; set; }
        public int Id_Res { get; set; }
        public string Name_Dis { get; set; }
        public int Id_Type { get; set; }

        public virtual customer customer { get; set; }
        public virtual order order { get; set; }
        public virtual type_dishes type_dishes { get; set; }
    }
}

这里我填写第一个表，一切正常，第一个表已填写。

public void InsertCustomer(customer customerDataContract)
        {
            //MySQLEntities Cust = new MySQLEntities();
            customer cust = new customer();
            {
                cust.Id_Cus = Convert.ToInt32(customerDataContract.Id_Cus);
                cust.FirstName_Cus = customerDataContract.FirstName_Cus;
                cust.LastName_Cus = customerDataContract.LastName_Cus;
                cust.PhoneNum_Cus = Convert.ToInt32(customerDataContract.PhoneNum_Cus);
                cust.Email_Cus = customerDataContract.Email_Cus;
            };
            dc.customers.Add(cust);
            dc.SaveChanges();

接下来是问题。第一个表已满，但在Id_Cus字段的第二个表中未放置任何值。据我了解，由于这些表是相互连接的，因此我希望在第一个表中填充该字段时也填充第二个表中的Id_Cus字段。我尝试按照下面的代码所示进行操作，但未成功，您能提出一些建议吗？

 public void InsertCustomer(customer customerDataContract)
        {
            //MySQLEntities Cust = new MySQLEntities();
            customer cust = new customer();
            {
                cust.Id_Cus = Convert.ToInt32(customerDataContract.Id_Cus);
                cust.FirstName_Cus = customerDataContract.FirstName_Cus;
                cust.LastName_Cus = customerDataContract.LastName_Cus;
                cust.PhoneNum_Cus = Convert.ToInt32(customerDataContract.PhoneNum_Cus);
                cust.Email_Cus = customerDataContract.Email_Cus;
            };
            dc.customers.Add(cust);


            customerpreference custPref = new customerpreference()
            {
                Id_Cus = customerDataContract.Id_Cus,
                Id_Res = 0, // some value
                Name_Dis = null, // some value
                Id_Type = 0 // some value
            };
            dc.customerpreferences.Add(custPref);

            dc.SaveChanges();

            int k = Convert.ToInt32(cust.Id_Cus);
            customer custFromDb =(from n in dc.customers
                                  where n.Id_Cus == k
                                  select n).Include(c => c.customerpreference).First();


        }