3 方式多对多流利 api

Question

我想使用代码优先和流畅的方式创建具有 3 种关系的数据库表 api。

在我设计的例子中，一个团队应该有一只猫、一只狗和一只猪的独特组合。另一个团队可能包含相同的 Cat 和 Pig，但不是相同的 Dog 等等。

首先，我希望能够获得包含特定动物的团队。 myCat.Teams() 如果可能的话，我也想强制执行唯一性。

public class Cat
{
    public int Id { get; set; }
    public virtual ICollection<Team> Teams { get; set; }
}
public class Dog
{
    public int Id { get; set; }
   public virtual ICollection<Team> Teams { get; set; }
}
public class Pig
{
    public Guid { get; set; }
   public virtual ICollection<Team> Teams { get; set; }
}

public class Team
{
    public int Id { get; set; }
    public int CatId { get; set; }
    public int DogId { get; set; }
    public Guid PigId { get; set; }

    public virtual Cat Cat {get; set;}
    public virtual Dog Dog {get; set;}
    public virtual Pig Pig {get; set;}
}

在 OnModelCreating() 中，为这些对象（CatMap、DogMap、PigMap、TeamMap）添加了 EntityTypeConfigurations。

我已经尝试从 TeamMap class 或从另一个方向设置 HasMany 关系。例如，在 DogMap 中：

        HasMany(t => t.Teams)
        .WithRequired(t => t.Dog)
        .HasForeignKey(t => t.DogId);

但是每当我尝试添加迁移时，我都会收到如下错误：

tSystem.Data.Entity.Edm.EdmAssociationConstraint: : 关系约束中从属角色和主要角色中的属性数必须相同。

如何正确设置这些关联以实现上述两个目标？谢谢！！

Answer 1

团队 class 不应有自己的 ID，因为主键是 Cat、Dog、Pig 的组合。所以，它应该是这样的：

public class Team
{

    public int CatId { get; set; }

    public int DogId { get; set; }

    public Guid PigId { get; set; }

    public virtual Cat Cat { get; set; }
    public virtual Dog Dog { get; set; }
    public virtual Pig Pig { get; set; }
}

映射：

protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
    //primary key, composed by a combination
    modelBuilder.Entity<Team>()
        .HasKey(i => new { i.CatId, i.DogId, i.PigId });

    modelBuilder.Entity<Team>()
        .HasRequired(i => i.Cat)
        .WithMany(i => i.Teams)
        .HasForeignKey(i => i.CatId)
        .WillCascadeOnDelete(false);

    modelBuilder.Entity<Team>()
        .HasRequired(i => i.Dog)
        .WithMany(i => i.Teams)
        .HasForeignKey(i => i.DogId)
        .WillCascadeOnDelete(false);

    modelBuilder.Entity<Team>()
        .HasRequired(i => i.Pig)
        .WithMany(i => i.Teams)
        .HasForeignKey(i => i.PigId)
        .WillCascadeOnDelete(false);

    base.OnModelCreating(modelBuilder);
}

生成的迁移：

CreateTable(
    "dbo.Teams",
    c => new
        {
            CatId = c.Int(nullable: false),
            DogId = c.Int(nullable: false),
            PigId = c.Guid(nullable: false),
        })
    .PrimaryKey(t => new { t.CatId, t.DogId, t.PigId })
    .ForeignKey("dbo.Cats", t => t.CatId, cascadeDelete: true)
    .ForeignKey("dbo.Dogs", t => t.DogId, cascadeDelete: true)
    .ForeignKey("dbo.Pigs", t => t.PigId, cascadeDelete: true)
    .Index(t => t.CatId)
    .Index(t => t.DogId)
    .Index(t => t.PigId);

CreateTable(
    "dbo.Cats",
    c => new
        {
            Id = c.Int(nullable: false, identity: true),
        })
    .PrimaryKey(t => t.Id);

CreateTable(
    "dbo.Dogs",
    c => new
        {
            Id = c.Int(nullable: false, identity: true),
        })
    .PrimaryKey(t => t.Id);

CreateTable(
    "dbo.Pigs",
    c => new
        {
            PigId = c.Guid(nullable: false),
        })
    .PrimaryKey(t => t.PigId);

如果因为某些原因Team必须有自己的Id；更改模型如下：

public class Team
{

    public int TeamId { get; set; }

    //....
}

映射：

modelBuilder.Entity<Team>()
    .HasKey(i => i.TeamId);

//if you want to make the teamId an auto-generated column
modelBuilder.Entity<Team>()
     .Property(i => i.TeamId).HasDatabaseGeneratedOption(DatabaseGeneratedOption.Identity);

//if you want to make the cat, dog, and pig combination unique
modelBuilder.Entity<Team>()
    .Property(i => i.CatId)
    .HasColumnAnnotation(IndexAnnotation.AnnotationName,
    new IndexAnnotation(
        new IndexAttribute("IX_TeamComp", 1) { IsUnique = true }));

modelBuilder.Entity<Team>()
    .Property(i => i.DogId)
    .HasColumnAnnotation(IndexAnnotation.AnnotationName,
    new IndexAnnotation(
        new IndexAttribute("IX_TeamComp",2) { IsUnique = true }));

modelBuilder.Entity<Team>()
    .Property(i => i.PigId)
    .HasColumnAnnotation(IndexAnnotation.AnnotationName,
    new IndexAnnotation(
        new IndexAttribute("IX_TeamComp", 3) { IsUnique = true }));

3 方式多对多流利 api

3 way many to many with fluent api

c#

entity-framework

fluent

associations