Question

我有两个Class Customers和MembershipType，并且有一个结构。创建数据库时，MembershipType列的值为null。我该如何解决？

## Guess the Right Number ##

#!/bin/bash
clear

while :

do

echo "enter the guessing number:"

read num

if [ $num -eq 47 ]; then

echo "That is a right number"

break

elif [ $num -le 47 ]; then

echo "print higher number"

elif [ $num -ge 47 ]; then

echo "print lower number"

fi

done

客户表

public class Customer
{
    public int CustomerId { get; set; }
    [Required]
    public string CustomerName { get; set; }
    [Required]
    public string CustomerGender { set; get; }
    public byte Age { set; get; }
    public bool IsSubscribedToNewsLetter { set; get; }
    public MembershipType MembershipType{ get; set; }
    public byte MembershipTypeId { set; get; }
}


public class MembershipType
{
    [Key]
    public byte MemebershipId { set; get; }
    public short SignUpFee{ get; set; }
    public byte DurationInMonth { set; get; }
    public byte DiscountRate { get; set; }
}

迁移：

  CusId CustName  CusGender Age  IsSub.. MembershipTypeId  MemberShipType_Membershipid
   1     Jobin       Male    27      0          2            NULL

Answer 1

我看到了几个可能的问题。

尝试一致的拼写... 客户具有“MembershipTypeId”外键，但“MembershipType”的主键是“MemembershipId”。如果您使用MembershipType MembershipTypeId的密钥会发生什么？ EF的基于约定的配置会变得混乱吗？
EF并不真正喜欢一对一的关系...当它创建它们时，它希望依赖的主键与主http://www.entityframeworktutorial.net/code-first/configure-one-to-one-relationship-in-code-first.aspx的主键具有相同的值

Answer 2

将MembershipTypeId和Customer中MembershipType字段的类型更改为int，删除现有迁移并再次添加新迁移，然后选择{ {1}}字段作为外键

否则，您必须在Context类

中使用Fluent API声明关系

Answer 3

您可以按如下方式解决问题：在[Required]上方MembershipTypeId以及[ForeignKey("MembershipTypeId")]属性上方MembershipType

public class Customer
{
   public int CustomerId { get; set; }
   [Required]
   public string CustomerName { get; set; }
   [Required]
   public string CustomerGender { set; get; }
   public byte Age { set; get; }
   public bool IsSubscribedToNewsLetter { set; get; }

   [Required]
   public byte MembershipTypeId { set; get; }

   [ForeignKey("MembershipTypeId")]
   public MembershipType MembershipType { get; set; }
}


public class MembershipType
{
   [Key]
   public byte MemebershipId { set; get; }
   public short SignUpFee { get; set; }
   public byte DurationInMonth { set; get; }
   public byte DiscountRate { get; set; }
}

更新

最好删除此迁移并创建一个新的，因为实体可能会丢失。

首先使用EF代码的数据库关系中的空值

3 个答案:

更新