在实体框架上建立外键关系的问题 [英] Problems creating a Foreign-Key relationship on Entity Framework

问题描述

以下是报告的负责人：

  public class Testata 
 {
 public Testata（）{Details = new List< Dettaglio>（）; } 
 public virtual int IDTEST {get;组; } 
 public virtual string Value {get;组; } 
 public virtual int IDDETAIL {get;组; } 
 public virtual string IDTE组; } 
 public virtual byte [] BLOB {get;组; } 
 
 public virtual IList< Dettaglio>细节{get;组; 
} 
  

这是报表的细节

  public class Dettaglio 
 {
 public virtual int IDDETAIL {get;组; } 
 public virtual int IDTEST {get;组; } 
 public virtual string DSDETAIL {get;组; } 
 
 public virtual Testata TEST_TABLE {get;组; } 
} 
  

这是我这两个流畅的API定义。报告负责人：

  public TEST_TABLEMap（）
 {
 //主键
 this.HasKey（t => t.IDTEST）
 .Property（t => t.IDTEST）
 .IsRequired（）
 .HasColumnType（Int）
 .HasDatabaseGeneratedOption（DatabaseGeneratedOption.Identity）
 .HasColumnName（IDTEST）; 
 
 
 // Table&列映射
 this.ToTable（TEST_TABLE）; 
 this.Property（t => t.Value）.HasColumnName（DSVALUETEST）; 
 this.Property（t => t.IDTE台）.HasColumnName（IDTE台）; 
 this.Property（t => t.BLOB）.HasColumnName（BLOB）; 
} 
  

报表详细信息：

  public TEST_DETAILMap（）
 {
 //主键
 this.HasKey（t => t.DSDETAIL）; 
 
 //属性
 this.Property（t => t.DSDETAIL）; 
 
 // Table&列映射
 this.ToTable（TEST_DETAIL）; 
 this.Property（t => t.IDDETAIL）.HasColumnName（IDDETAIL）; 
 // this.Property（t => t.IDTEST）.HasColumnName（IDTEST）; 
 this.Property（t => t.DSDETAIL）.HasColumnName（DSDETAIL）; 
 
 //关系
 this.HasOptional（t => t.TEST_TABLE）
 .WithMany（t => t.Details）
 .HasForeignKey（d = d.IDDETAIL）.WillCascadeOnDelete（true）; 
 
} 
  

执行时我总是得到这个错误

System.Data.Entity.Edm.EdmAssociationType：：与Dettaglio_TEST_TABLE关系中角色Dettaglio_TEST_TABLE_Target中的参照约束的多重性冲突。因为从属角色中的所有属性都不可为空，所以主体角色的多重性必须为1。

我猜，这意味着我在外键定义方面失败了，但我真的不知道在哪里看。
任何帮助/提示都不胜感激。

解决方案

您的外键属性在 Dettaglio ...

  public virtual int IDTEST {get;组; } 
  

...它有一个不可空的类型（ int ），因此不能是可选的，并且您的映射...

  this.HasOptional（t => t .TEST_TABLE）// ... 
  

...您希望关系是可选的。 / p>



如果您确实想要一个可选关系使用可空的FK属性：

  public virtual int？ IDTEST {get;组; 
  

否则，您必须使用 HasRequired 需要与不可空FK属性的关系。

i'm having trouble configuring a foreign key relationship in my Entity Framework fluent Api:

Here is the head of the report:

 public class Testata
{
    public Testata() { Details = new List<Dettaglio>(); }
    public virtual int IDTEST { get; set; }
    public virtual string Value { get; set; }
    public virtual int IDDETAIL { get; set; }
    public virtual string IDTESTALT { get; set; }
    public virtual byte[] BLOB { get; set; }

    public virtual IList<Dettaglio> Details { get; set; }
}

This is the report's detail

public class Dettaglio
{
    public virtual int IDDETAIL { get; set; }
    public virtual int IDTEST { get; set; }
    public virtual string DSDETAIL { get; set; }

    public virtual Testata TEST_TABLE { get; set; }
}

And this is my fluent API definition of both. Head of the report:

public TEST_TABLEMap()
    {
        // Primary Key
        this.HasKey(t => t.IDTEST)
            .Property(t => t.IDTEST)
            .IsRequired()
            .HasColumnType("Int")
            .HasDatabaseGeneratedOption(DatabaseGeneratedOption.Identity)
            .HasColumnName("IDTEST");


        // Table & Column Mappings
        this.ToTable("TEST_TABLE");
        this.Property(t => t.Value).HasColumnName("DSVALUETEST");
        this.Property(t => t.IDTESTALT).HasColumnName("IDTESTALT");
        this.Property(t => t.BLOB).HasColumnName("BLOB");
    }

Detail of the report:

public TEST_DETAILMap()
    {
        // Primary Key
        this.HasKey(t => t.DSDETAIL);

        // Properties
        this.Property(t => t.DSDETAIL);

        // Table & Column Mappings
        this.ToTable("TEST_DETAIL");
        this.Property(t => t.IDDETAIL).HasColumnName("IDDETAIL");
        // this.Property(t => t.IDTEST).HasColumnName("IDTEST");
        this.Property(t => t.DSDETAIL).HasColumnName("DSDETAIL");

        // Relationships
        this.HasOptional(t => t.TEST_TABLE)
            .WithMany(t => t.Details)
            .HasForeignKey(d => d.IDDETAIL).WillCascadeOnDelete(true);

    }

On execution i always get this error

System.Data.Entity.Edm.EdmAssociationType: : Multiplicity conflicts with the referential constraint in Role 'Dettaglio_TEST_TABLE_Target' in relationship 'Dettaglio_TEST_TABLE'. Because all of the properties in the Dependent Role are non-nullable, multiplicity of the Principal Role must be '1'.

Which, i guess, means i'm failing something at foreign key definition, but i don't really know where to look at. Any help/hint is much appreciated.

解决方案

There is a conflict between your foreign key property in class Dettaglio...

public virtual int IDTEST { get; set; }

...which has a non-nullable type (int) and therefore cannot be optional and your mapping...

this.HasOptional(t => t.TEST_TABLE) //...

...where you want the relationship to be optional.

If you indeed want an optional relationship use a nullable FK property:

public virtual int? IDTEST { get; set; }

Otherwise you must use HasRequired for a required relationship with a non-nullable FK property.

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