代码优先INSERT语句与FOREIGN KEY约束冲突 [英] Code first The INSERT statement conflicted with the FOREIGN KEY constraint

问题描述

我刚开始使用Code first方法来创建数据库。我有以下3个表：

公共类TagDatabase 
 {
 [Key] 
 [DatabaseGenerated（ DatabaseGeneratedOption.Identity）] 
 public int TagID {get;组; } 
公共字符串TagName {get;组; } 
 public string说明{get;组; } 
 public int Count {get;组; } 
 
 [ForeignKey（TagTypes）] 
 public virtual int TagTypeID {get;组; } 
 public virtual ICollection< tagtypesdb> TagTypes {get;组; } 
 
 [ForeignKey（Users）] 
 public virtual int CreatedBy {get;组; } 
 public virtual UsersDb Users {get;组; } 
} 
 
公共类TagTypesDb 
 {
 [Key] 
 [DatabaseGenerated（DatabaseGeneratedOption.Identity）] 
 public int TagTypeID {get ;组; } 
公共字符串TagTypeName {get;组; } 
} 
 
公共类UsersDb 
 {
 [Key] 
 [DatabaseGenerated（DatabaseGeneratedOption.Identity）] 
 public int UserID {get ;组; } 
公共字符串UserName {get;组; } 
} 

这里AccountHolder和Nominee都有1到*的地址替换。我用于此的流畅API代码是：

  protected  覆盖  void  OnModelCreating（DbModelBuilder modelBuilder）
 {
 modelBuilder.Entity< tagdatabase>（）
 .HasOptional （a = >  a.TagTypes）
 .WithMany（）
 .HasForeignKey（u =  >  u.TagTypeID）; 
 
 modelBuilder.Entity< tagdatabase>（）
 .HasRequired（a = >  a.Users）
。 WithMany（）
 .HasForeignKey（u = >  u.CreatedBy）; 
} 

现在我的问题是每当我试图在AccountHolder或Nominee中插入数据时我都有这个例外：

 TagDatabase_TagTypes ::多重性与关系TagDatabase_TagTypes中Role'TagDatabase_TagTypes_Target'中的引用约束冲突。因为从属角色中的所有属性都是不可为空的，所以主要角色的多样性必须为1。

有人可以告诉我如何解决这个问题我在这里缺少什么？

解决方案

你的流利API有TagTypes选项

引用：

HasOptional（a => a.TagTypes）

但是在模型外键关系似乎是强制性的。要么将Hasoptional更改为强制，要么在模型中使其可以为空。

 public int？ TagTypeID {get;设置;} 

和/或

 public int？ CreatedBy {get;设置;} 

I just started using Code first approach for creating databases. I have following 3 tables :

public class TagDatabase
{
    [Key]
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public int TagID { get; set; }
    public string TagName { get; set; }
    public string Description { get; set; }
    public int Count { get; set; }

    [ForeignKey("TagTypes")]
    public virtual int TagTypeID { get; set; }
    public virtual ICollection<tagtypesdb> TagTypes { get; set; }

    [ForeignKey("Users")]
    public virtual int CreatedBy { get; set; }
    public virtual UsersDb Users { get; set; }
}

public class TagTypesDb
{
    [Key]
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public int TagTypeID { get; set; }
    public string TagTypeName { get; set; }
}

public class UsersDb
{
    [Key]
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public int UserID { get; set; }
    public string UserName { get; set; }
}

Here AccountHolder and Nominee both have 1 to * replationship with the address. The fluent API code which i used for this is :

protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
   modelBuilder.Entity<tagdatabase>()
           .HasOptional(a => a.TagTypes)
           .WithMany()
           .HasForeignKey(u => u.TagTypeID);

   modelBuilder.Entity<tagdatabase>()
           .HasRequired(a => a.Users)
           .WithMany()
           .HasForeignKey(u => u.CreatedBy);
}

Now my issue is whenever i am trying to insert data in AccountHolder or Nominee i got this exception :

TagDatabase_TagTypes: : Multiplicity conflicts with the referential constraint in Role 'TagDatabase_TagTypes_Target' in relationship 'TagDatabase_TagTypes'. Because all of the properties in the Dependent Role are non-nullable, multiplicity of the Principal Role must be '1'.

Can anybody please tell me how to solve this issue and what i am missing here ?

解决方案

Your fluent API has TagTypes option

Quote:

HasOptional(a => a.TagTypes)

But in the model foreign key relationship seems to be mandatory .Either change the Hasoptional to mandatory or make it nullable in the model.

public int? TagTypeID { get; set;}

and/or

public int? CreatedBy { get; set;}

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