具有多个可选一对一关系的实体框架表 [英] Entity Framework table with multiple optional one to one relationships

问题描述

这里有几个问题，但是没有一个对我有太大帮助，所以我决定问自己一个问题。

There are a few questions out there but none of them have been much help to me so I decided to ask my own.

我想先使用Entity Framework代码创建一个奇怪的关系。我有三个实体（资格，测试和程序）所有人都可以选择拥有文件。我正在尝试将所有文​​档存储在一张表中。如何配置所有这些实体之间的关系。

I want to use Entity Framework code first to create a strange relationship. I have three entities (Qualification, Test and Procedure) that all have the option of having a document(s). I am attempting to store all the documents in one table. How do I configure the relationship between all these entities.

• 资格有一个一个可选的 Document


• Test 具有一对一的可选文档


• 过程有一对多的可选 Documents

• Qualification has one to one optional Document
• Test has one to one optional Document
• Procedure has one to many optional Documents

文档与一个<$ c具有必需的关系$ c>资格，测试或程序。

public class Assessment
{
    public int AssessmentId { get; set; }
    //Other properties in Assessment
    public Document Document { get; set; }
}

public class Qualification
{
    public int QualificationId{ get; set; }
    //Other properties in Qualification
    public Document Document { get; set; }
}

public class Procedure
{
    public int ProcedureId { get; set; }
    //Other properties in Procedure
    public ICollection<Document> Documents { get; set; }
}

public class Document
{
    public int DocumentId { get; set; }
    //Other properties in Document
    public Qualification Qualification { get; set; }
    public Assessment Assessment { get; set; }
    public Procedure Procedure { get; set; }
}

protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
    // Not sure what goes here, but this was not working 
    modelBuilder.Entity<Document>()
        .HasOptional(d => d.Qualification).WithOptionalPrincipal(q => q.Document);

    modelBuilder.Entity<Document>()
        .HasOptional(d => d.Asssessment).WithOptionalPrincipal(q => q.Document);
}

添加迁移时出现错误：

无法确定类型之间关联的主体。必须使用关系流利的API或数据注释来显式配置此关联的主体端。

Unable to determine the principal end of an association between the types. The principal end of this association must be explicitly configured using either the relationship fluent API or data annotations.

我不确定该怎么做这个。我在评估和资格中具有可为空的int DocumentId b / c 过程可以保存集合，因此 Document 必须保留ID。 Document 是否为每个可能的父项保留一个可为空的ID？

I am not sure how to do this. I had a nullable int DocumentId in Assessment and Qualification but that will not work b/c Procedure can hold a collection so Document must hold the Id. Does Document hold a nullable Id for each possible parent? Help please.

推荐答案

在映射中，您将 Document 设置为主体，但实际上这是依赖的。因此，您应该将映射更改为：

In your mappings you set Document as principal, but in reality it is the dependent. So you should change your mappings to:

modelBuilder.Entity<Document>()
    .HasRequired(d => d.Qualification)
    .WithOptionalDependent(q => q.Document);

modelBuilder.Entity<Document>()
    .HasRequired(d => d.Asssessment)
    .WithOptionalDependent(q => q.Document);

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