c# - 实体框架代码优先：在数据库中插入 NULL 值

Question

我正在使用实体框架代码优先方法。我有以下代码将数据插入到 PaymentComponent 和 Payment 表中。插入 PaymentComponent 表的数据不正确。即使域对象中的相应属性不为空，它在两列（对于一条记录）中都有 NULL 值。需要进行哪些更改才能使其正常工作？

编辑

当我在 NerdDinners 类中添加以下内容时，我得到以下结果 - 它有新的不需要的列

  public DbSet<ClubCardPayment> ClubCardPayments { get; set; }

原始代码

static void Main(string[] args)
{
    string connectionstring = "Data Source=.;Initial Catalog=NerdDinners;Integrated Security=True;Connect Timeout=30";

    using (var db = new NerdDinners(connectionstring))
    {
        GiftCouponPayment giftCouponPayment = new GiftCouponPayment();
        giftCouponPayment.MyValue=250;
        giftCouponPayment.MyType = "GiftCouponPayment";

        ClubCardPayment clubCardPayment = new ClubCardPayment();
        clubCardPayment.MyValue = 5000;
        clubCardPayment.MyType = "ClubCardPayment";


        List<PaymentComponent> comps = new List<PaymentComponent>();
        comps.Add(giftCouponPayment);
        comps.Add(clubCardPayment);

        var payment = new Payment { PaymentComponents = comps, PayedTime=DateTime.Now };
        db.Payments.Add(payment);

        int recordsAffected = db.SaveChanges();

    }
}

域名代码

public abstract class PaymentComponent
{
    public int PaymentComponentID { get; set; }
    public abstract int MyValue { get; set; }
    public abstract string MyType { get; set; }
    public abstract int GetEffectiveValue();
}


public partial class GiftCouponPayment : PaymentComponent
{

    private int couponValue;
    private string myType;

    public override int MyValue
    {
        get
        {
            return this.couponValue;
        }
        set
        {
            this.couponValue = value;
        }
    }

    public override string MyType
    {
        get
        {
            return this.myType;
        }
        set
        {
            this.myType = value;
        }
    }

    public override int GetEffectiveValue()
    {
        if (this.PaymentComponentID < 2000)
        {
            return 0;
        }
        return this.couponValue;
    }

}


public partial class ClubCardPayment : PaymentComponent
{

    private int cardValue;
    private string myType;

    public override int MyValue
    {
        get
        {
            return this.cardValue;
        }
        set
        {
            this.cardValue = value;
        }
    }

    public override string MyType
    {
        get
        {
            return this.myType;
        }
        set
        {
            this.myType = value;
        }
    }

    public override int GetEffectiveValue()
    {
        return this.cardValue;
    }

}

public partial class Payment
{
    public int PaymentID { get; set; }
    public List<PaymentComponent> PaymentComponents { get; set; }
    public DateTime PayedTime { get; set; }

}



//System.Data.Entity.DbContext is from EntityFramework.dll
public class NerdDinners : System.Data.Entity.DbContext
{

    public NerdDinners(string connString): base(connString)
    { 

    }

    protected override void OnModelCreating(DbModelBuilder modelbuilder)
    {
        modelbuilder.Conventions.Remove<PluralizingTableNameConvention>();
    }


    public DbSet<GiftCouponPayment> GiftCouponPayments { get; set; }
    public DbSet<Payment> Payments { get; set; }

}

参考：

1. 使用实体框架代码优先映射属性分隔表时，移动外键字段
2. 覆盖实体框架实体属性
3. EntityFramework 如何覆盖属性
4. http://weblogs.asp.net/manavi/archive/2011/04/24/associations-in-ef-4-1-code-first-part-4-table-splitting.aspx
5. http://www.robbagby.com/entity-framework/entity-framework-modeling-entity-splitting/
6. 实体框架映射方案 - http://msdn.microsoft.com/en-us/library/cc716779.aspx
7. http://blogs.microsoft.co.il/blogs/gilf/archive/2009/03/06/entity-splitting-in-entity-framework.aspx

Answer 1

您尚未在数据上下文中定义 ClubCardPayment 数据库集。

插入这个，它应该可以工作

public DbSet<ClubCardPayment> ClubCardPayments { get; set; }

Answer 2

直接在基类中MyType实现。MyValueEF 允许共享成员仅在基类中实现。在派生类中实现的成员在结果表中使用它们自己的列。

Answer 3

您需要定义实际实现抽象类的 2 个类，这是 EF 了解不同类以及如何读取/更新/写入它们的实例的唯一方法。

（无需在 EF 中映射抽象类！）。

Answer 4

这对您的问题没有帮助，而只是我这边的一个提示：
为什么要在派生类中显式地实现 MyValue 和 MyType ？如果实现始终相同，则可以将其放入抽象类中...