实体框架能否生成从外键到父表中 GUID 的映射？

Question

我的数据库有两个这样的表（为了简单起见，删除了一些列）

CREATE TABLE [dbo].[Question] (
    [QuestionId]       INT              IDENTITY (1, 1) NOT NULL,
    [ProblemId]        INT              NOT NULL,
    [QuestionUId]      UNIQUEIDENTIFIER DEFAULT (newid()) NOT NULL,
    CONSTRAINT [PK_Question] PRIMARY KEY CLUSTERED ([QuestionId] ASC)
);

CREATE UNIQUE NONCLUSTERED INDEX [Question_QuestionUId_UIX]
    ON [dbo].[Question]([QuestionUId] ASC);

CREATE TABLE [dbo].[AdminTestQuestion] (
    [AdminTestQuestionId] INT              IDENTITY (1, 1) NOT NULL,
    [AdminTestId]         INT              NOT NULL,
    [QuestionNumber]      INT              NOT NULL,
    [QuestionUId]         UNIQUEIDENTIFIER NOT NULL,
    CONSTRAINT [PK_AdminTestQuestion] PRIMARY KEY CLUSTERED ([AdminTestQuestionId] ASC),
    CONSTRAINT [FK_AdminTestQuestionQuestionUId] FOREIGN KEY ([QuestionUId]) REFERENCES [dbo].[Question] ([QuestionUId])
);

当我运行实体框架逆向工程时，它不会从 AdminTestQuestion 创建映射 > 问题 并且它不会在 Question 类中创建 AdminTestQuestions 的集合。我希望看到这样的东西，但据我了解，当外键的一端是 GUID 时，它会遇到困难。

public partial class Question
{
    public Question()
    {
        this.Answers = new List<AdminTestQuestion>();
    }
    public int QuestionId { get; set; }
    public int ProblemId { get; set; }
    public System.Guid QuestionUId { get; set; }
}

我还希望在 AdminTestQuestion 映射文件中出现类似这样的映射信息：

        this.HasRequired(t => t.QuestionUId)
            .With????(t => t.Questions)
            .HasForeignKey(d => d.QuestionUId);

谁能告诉我我可以用 EF6+ 创建这种到 GUID 的映射吗？

Answer 1

EF6 无法做到这一点，因为它不知道 QuestionUId 列上的唯一索引。做到这一点的唯一方法是让 QuestionUId 成为 Question 表中的主键，我认为没有什么可以阻止您这样做：

CREATE TABLE [dbo].[Question] (
    [QuestionId]       INT              IDENTITY (1, 1)  NOT NULL,
    [ProblemId]        INT              NOT NULL,
    [QuestionUId]      UNIQUEIDENTIFIER DEFAULT (newid()) NOT NULL,
    CONSTRAINT [PK_Question] PRIMARY KEY CLUSTERED ([QuestionUId] ASC)
);

CREATE TABLE [dbo].[AdminTestQuestion] (
    [AdminTestQuestionId] INT              IDENTITY (1, 1) NOT NULL,
    [AdminTestId]         INT              NOT NULL,
    [QuestionNumber]      INT              NOT NULL,
    [QuestionUId]         UNIQUEIDENTIFIER NOT NULL,
    CONSTRAINT [PK_AdminTestQuestion] PRIMARY KEY CLUSTERED ([AdminTestQuestionId] ASC),
    CONSTRAINT [FK_AdminTestQuestionQuestionUId] FOREIGN KEY ([QuestionUId]) REFERENCES [dbo].[Question] ([QuestionUId])
);

哪个生成（使用数据库中的 Code First）：

public partial class Question
{
    public Question()
    {
        AdminTestQuestion = new HashSet<AdminTestQuestion>();
    }
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public int QuestionId { get; set; }
    public int ProblemId { get; set; }
    [Key]
    public Guid QuestionUId { get; set; }
    public virtual ICollection<AdminTestQuestion> AdminTestQuestion { get; set; }
}

public partial class AdminTestQuestion
{
    public int AdminTestQuestionId { get; set; }
    public int AdminTestId { get; set; }
    public int QuestionNumber { get; set; }
    public Guid QuestionUId { get; set; }
    public virtual Question Question { get; set; }
}


protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
    modelBuilder.Entity<Question>()
    .HasMany(e => e.AdminTestQuestion)
    .WithRequired(e => e.Question)
    .WillCascadeOnDelete(false);
}