C# 在实体框架上创建外键关系的问题
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/17420064/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
Problems creating a Foreign-Key relationship on Entity Framework
提问by user2541621
i'm having trouble configuring a foreign key relationship in my Entity Framework fluent Api:
我在我的 Entity Framework fluent Api 中配置外键关系时遇到问题：
Here is the head of the report:
这是报告的标题：
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
这是报告的详细信息
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:
这是我对两者的流畅 API 定义。报告负责人：
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:
报告详情：
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
在执行时，我总是收到此错误
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'.
System.Data.Entity.Edm.EdmAssociationType:: 多重性与关系“Dttaglio_TEST_TABLE”中的角色“Dettaglio_TEST_TABLE_Target”中的参照约束冲突。因为从属角色中的所有属性都是不可为空的，所以主体角色的多重性必须为“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.
我想，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。非常感谢任何帮助/提示。
回答by Slauma
There is a conflict between your foreign key property in class Dettaglio...
您在课堂上的外键属性之间存在冲突Dettaglio...
public virtual int IDTEST { get; set; }
...which has a non-nullable type (int) and therefore cannot be optional and your mapping...
...具有不可为空的类型 ( int)，因此不能是可选的，并且您的映射...
this.HasOptional(t => t.TEST_TABLE) //...
...where you want the relationship to be optional.
...您希望关系是可选的。
If you indeed want an optional relationship use a nullable FK property:
如果您确实想要一个可选关系，请使用可为空的 FK 属性：
public virtual int? IDTEST { get; set; }
Otherwise you must use HasRequiredfor a required relationship with a non-nullable FK property.
否则，您必须使用HasRequired不可为空的 FK 属性的必需关系。
