与E.F.码首先一到零或一的关系，当列不是主键 [英] One-to-Zero-or-One relationship with E.F. Code First when column is not primary key

问题描述

我开发一个实体框架6.1.3代码优先库，C＃和.NET Framework 4.5.1。

I'm developing an Entity Framework 6.1.3 Code First library, C# and .NET Framework 4.5.1.

我有一到一个问题-Zero-或一的关系（或者是另一种关系）。

I have a problem with a One-to-Zero-or-One relationship (or maybe is another kind of relationship).

我有两个表，代码和 HelperCodes ，代码可以有零个或一个助手代码。这是SQL脚本创建这两个表和它们之间的关系：

I have two tables, Codes and HelperCodes, a code could have zero or one helper code. This is the sql script to create these two tables and their relationships:

CREATE TABLE [dbo].[Code]
(
    [Id] NVARCHAR(20) NOT NULL, 
    [Level] TINYINT NOT NULL, 
    [CommissioningFlag] TINYINT NOT NULL, 
    [SentToRanger] BIT NOT NULL DEFAULT 0, 
    [LastChange] NVARCHAR(50) NOT NULL, 
    [UserName] NVARCHAR(50) NOT NULL, 
    [Source] NVARCHAR(50) NOT NULL, 
    [Reason] NVARCHAR(200) NULL, 
    [HelperCodeId] NVARCHAR(20) NULL,
    CONSTRAINT [PK_Code] PRIMARY KEY CLUSTERED
    (
        [Id] ASC
    ),
    CONSTRAINT [FK_Code_LevelConfiguration]
       FOREIGN KEY ([Level])
        REFERENCES [dbo].[LevelConfiguration] ([Level]),
    CONSTRAINT [FK_Code_HelperCode]
       FOREIGN KEY ([HelperCodeId])
        REFERENCES [dbo].[HelperCode] ([HelperCodeId])
)

CREATE TABLE [dbo].[HelperCode]
(
    [HelperCodeId] NVARCHAR(20) NOT NULL, 
    [Level] TINYINT NOT NULL, 
    [CommissioningFlag] TINYINT NOT NULL, 
    [LastChange] NVARCHAR(50) NOT NULL,
    CONSTRAINT [PK_HelperCode] PRIMARY KEY CLUSTERED
    (
        [Id] ASC
    ),
    CONSTRAINT [FK_HelperCode_LevelConfiguration]
       FOREIGN KEY ([Level])
        REFERENCES [dbo].[LevelConfiguration] ([Level])
)

不过， ，当我尝试做相同的实体框架不这样做。我的问题是规范和HelperCodes foreing键

But, when I try to do the same with Entity Framework it doesn't do the same. My problem is in Codes and HelperCodes foreing key.

这是我的实体框架代码优先代码：

This is my Entity Framework Code First code:

public class Code
    {
        public string Id { get; set; }
        public byte Level { get; set; }

        // omitted for brevity

        public string HelperCodeId { get; set; }

        public virtual HelperCode HelperCode { get; set; }
    }

class CodeConfiguration : EntityTypeConfiguration<Code>
{
    public CodeConfiguration()
    {
        HasKey(c => c.Id);

        Property(c => c.Id)
            .HasDatabaseGeneratedOption(DatabaseGeneratedOption.None);

        Property(c => c.Id)
            .HasMaxLength(20);

        // omitted for brevity

        Property(c => c.HelperCodeId)
            .HasMaxLength(20)
            .IsOptional();

        HasOptional(c => c.HelperCode)
            .WithRequired(hc => hc.Code);
    }
}

public class HelperCode
{
    public string HelperCodeId { get; set; }
    public byte Level { get; set; }
    public byte CommissioningFlag { get; set; }
    public string LastChange { get; set; }

    public virtual Code Code { get; set; }
}

class HelperCodeConfiguration : EntityTypeConfiguration<HelperCode>
{
    public HelperCodeConfiguration()
    {
        HasKey(h => h.HelperCodeId);

        Property(h => h.HelperCodeId)
            .HasMaxLength(20);

        Property(h => h.Level)
            .IsRequired();

        Property(h => h.CommissioningFlag)
            .IsRequired();

        Property(h => h.LastChange)
            .IsOptional()
            .HasMaxLength(50);
    }
}

本实体的Code First的代码生成外键 HelperCodes 使用表 HelperCodes.HelperCodeId 引用 Codes.Id 。

This Entity Code First code generates a foreign key in HelperCodes table using HelperCodes.HelperCodeId referencing Codes.Id.

实体框架只允许这种关系如果两个表具有相同的主键。

Entity Framework only allows this kind of relationship if both tables have the same primary key.

有关如何任何想法？解决这个EF错误

Any idea about how to resolve this E.F. bug?

推荐答案

第一：删除 HelperCodeId 从在代码类：

public class Code
{
    public string Id { get; set; }
    public byte Level { get; set; }

    // omitted for brevity

    public virtual HelperCode HelperCode { get; set; }
}

在代码配置：

.HasOptional(i => i.HelperCode)
.WithRequired(i => i.Code);

生成迁移：

Generated migration:

CreateTable(
    "dbo.Codes",
    c => new
        {
            Id = c.String(nullable: false, maxLength: 128),
            Level = c.Byte(nullable: false),
        })
    .PrimaryKey(t => t.Id);

CreateTable(
    "dbo.HelperCodes",
    c => new
        {
            HelperCodeId = c.String(nullable: false, maxLength: 128),
            Level = c.Byte(nullable: false),
            CommissioningFlag = c.Byte(nullable: false),
            LastChange = c.String(),
        })
    .PrimaryKey(t => t.HelperCodeId)
    .ForeignKey("dbo.Codes", t => t.HelperCodeId)
    .Index(t => t.HelperCodeId);

只有 HelperCodes 表应具有国外。关键语句

Only the HelperCodes table should have the foreign key statement.

HelperCodeId 是主键，也是一个外键，所以它保证了0：1的关系。

HelperCodeId is a primary key and also a foreign key, so it ensures the 0:1 relationship.

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