实体框架 - 流畅的APi - 创建具有2个FK的表

问题描述

例如：

产品= StarWar

AssociatedProducts =第V集：帝国反击，第六集：绝地的回归，第七集：力量唤醒

但是EF会生成一些额外列的数据库。

这是我的产品类：

  public class Product 
 {
 public int Id {get;组; } 
 public string Name {get;组; } 
 public string ShortDescription {get;组; } 
 public string FullDescription {get;组; } 
 public decimal UnitPrice {get;组; } 
 ...... 
 public virtual ICollection< AssociatedProducts>相关产品{get;组; } 
 ... 
} 
  

这是我的AssociatedProduct类：

  public class AssociatedProducts 
 {
 public int Id {get;组; } 
 
 public int ProductId {get;组; } 
 public int AssociatedProductId {get;组; } 
 
 public int DisplayOrder {get;组; } 
 public DateTime CreatedOn {get;组; } 
 
 public virtual产品产品{get;组; } 
 public virtual Product AssociatedProductsId {get;组; 
} 
  

这是我对于AssocietedProduct类的映射：

  public AssociatedProductsMap（）
 {
 //主键
 HasKey（a => a.Id）; 
 
 //属性
属性（a => a.CreatedOn）.IsRequired（）; 
属性（a => a.ProductId）.IsRequired（）; 
属性（a => a.AssociatedProductId）.IsRequired（）; 
属性（a => a.DisplayOrder）.IsRequired（）; 
 
 //关系
 HasRequired（a => a.Products）
 .WithMany（p => p.Products）
 .HasForeignKey（a => ; a.ProductId）
 .WillCascadeOnDelete（false）; 
 
 HasRequired（a =&a .AssociatedProductsId）
 .WithMany（p => p.AssociatedProducts）
 .HasForeignKey（a => a.AssociatedProductId）
 .WillCascadeOnDelete（false）; 
 
 // Table 
 ToTable（AssociatedProducts）; 
} 
  

这是我如何播种：

  var associetedProducts = new List< AssociatedProducts> 
 {
 new AssociatedProducts {ProductId = 1，AssociatedProductId = 3，DisplayOrder = 1，CreatedOn = DateTime.Now}，
 new AssociatedProducts {ProductId = 1，AssociatedProductId = 4，DisplayOrder = CreatedOn = DateTime.Now}，
 new AssociatedProducts {ProductId = 1，AssociatedProductId = 5，DisplayOrder = 3，CreatedOn = DateTime.Now} 
} 
 
 new List< Product> 
 {
 new Product {Name =StarWar，ShortDescription =...，FullDescription =P .......，UnitPrice = 15m，AssociatedProducts = correletedProducts}，
 new Product {Name =StarWar Episode V，ShortDescription =...，FullDescription =P .......，UnitPrice = 15m}，
 new Product {Name =StarWar剧集VI，ShortDescription =...，FullDescription =P .......，UnitPrice = 15m}，
 new Product {Name =StarWar Episode VII，ShortDescription =.. ，FullDescription =P .......，UnitPrice = 15m}，
} .ForEach（a => context.Products.AddOrUpdate（a））; 
 
 context.SaveChanges（）; 
  

这是我期望从AssociatedProductsId表：
ID + ProductId（FK）+ AssociatedProductsId （FK）+ date + ......

但这是我得到的：

我的错误是什么？
这是一个关联产品的好方法吗？

解决方案

我认为你的课不正确。

1问题：为什么EF生成具有额外列的表？

在这种情况下，EF使用TPH策略。看看这个链接

2问题：我的错误是什么？这是一个关联产品的好方法吗？

您的映射应该是这样的：

  public class Product 
 {
 public int ProductId {get;组; } 
 
 public string Name {get;组; } 
 
 public virtual ICollection< ProductAssociation>相关产品{get;组; } 
 
 public virtual ICollection< ProductAssociation>产品介绍组; 
} 
 
 public class ProductAssociation 
 {
 public int ProductId {get;组; } 
 
 public int ProductAssociatedId {get;组; } 
 
 public DateTime CreationDate {get;组; } 
 
 public virtual Product Product {get;组; } 
 
 public virtual Product ProductAssociated {get;组; 
 
 
 public class上下文：DbContext 
 {
 public Context（）：base（Model2）
 {
 
} 
 
 public DbSet< Product>产品{get;组; } 
 public DbSet< ProductAssociation>产品协会{get;组; 
 
 protected override void OnModelCreating（DbModelBuilder modelBuilder）
 {
 modelBuilder.Entity< Product>（）
 .HasKey（i => i.ProductId）; 
 
 modelBuilder.Entity< ProductAssociation>（）
 .HasKey（i => new {i.ProductId，i.ProductAssociatedId}）; 
 
 modelBuilder.Entity< Product>（）
 .HasMany（i =&i; AssociatedProducts）
 .WithRequired（i => i.ProductAssociated）
 .HasForeignKey（i => i.ProductAssociatedId）
 .WillCascadeOnDelete（false）; 
 
 modelBuilder.Entity< Product>（）
 .HasMany（i =&i ;ProductsAssociatedThisProduct）
 .WithRequired（i => i.Product）
 .HasForeignKey（i => i.ProductId）
 .WillCascadeOnDelete（false）; 
 
 
 base.OnModelCreating（modelBuilder）; 
} 
 
 
} 
  

种子

  var product1 = new Product（）{Name =StarWars，ProductId = 1}; 
 
 var product2 = new Product（）{Name =StarWars II，ProductId = 2}; 
 
 context.ProductsAssociations.AddOrUpdate（new ProductAssociation {Product = product1，CreationDate = DateTime.Now，ProductAssociated = product2}）; 
 context.Products.AddOrUpdate（product1）; 
 context.Products.AddOrUpdate（product2）; 
 context.SaveChanges（）; 
  

I have this product class which has a list of products associated.

eg:

Product = StarWar

AssociatedProducts = Episode V: The Empire Strikes Back, Episode VI: Return of the Jedi, Episode VII: The Force Awakens

But EF generates the database with some extra columns.

This is my Product Class:

public class Product
{
    public int Id { get; set; }
    public string Name { get; set; }
    public string ShortDescription { get; set; }
    public string FullDescription { get; set; }
    public decimal UnitPrice { get; set; }
    ......
    public virtual ICollection<AssociatedProducts> AssociatedProducts { get; set; }
    ......
}

This is my AssociatedProduct Class:

public class AssociatedProducts
{
    public int Id { get; set; }

    public int ProductId { get; set; }
    public int AssociatedProductId { get; set; }

    public int DisplayOrder { get; set; }
    public DateTime CreatedOn { get; set; }

    public virtual Product Products { get; set; }
    public virtual Product AssociatedProductsId { get; set; }
}

This is my mapping for AssocietedProduct class:

public AssociatedProductsMap()
    {
        // Primary Key
        HasKey(a => a.Id);

        // Properties
        Property(a => a.CreatedOn).IsRequired();
        Property(a => a.ProductId).IsRequired();
        Property(a => a.AssociatedProductId).IsRequired();
        Property(a => a.DisplayOrder).IsRequired();

        //Relationship
        HasRequired(a => a.Products)
            .WithMany(p => p.Products)
            .HasForeignKey(a => a.ProductId)
            .WillCascadeOnDelete(false);

        HasRequired(a => a.AssociatedProductsId)
            .WithMany(p => p.AssociatedProducts)
            .HasForeignKey(a => a.AssociatedProductId)
            .WillCascadeOnDelete(false);

        //Table
        ToTable("AssociatedProducts");
    }

And this is how I am seeding:

var associetedProducts = new List<AssociatedProducts>
        {
            new AssociatedProducts {ProductId= 1, AssociatedProductId = 3, DisplayOrder = 1, CreatedOn = DateTime.Now},
            new AssociatedProducts {ProductId= 1, AssociatedProductId = 4, DisplayOrder = 2, CreatedOn = DateTime.Now},
            new AssociatedProducts {ProductId= 1, AssociatedProductId = 5, DisplayOrder = 3, CreatedOn = DateTime.Now}
        }

new List<Product>
        {
          new Product {Name = "StarWar", ShortDescription = "...", FullDescription = "P.......", UnitPrice = 15m, AssociatedProducts = associetedProducts},
          new Product {Name = "StarWar Episode V", ShortDescription = "...", FullDescription = "P.......", UnitPrice = 15m},
          new Product {Name = "StarWar Episode VI", ShortDescription = "...", FullDescription = "P.......", UnitPrice = 15m},
          new Product {Name = "StarWar Episode VII", ShortDescription = "...", FullDescription = "P.......", UnitPrice = 15m},
    }.ForEach(a => context.Products.AddOrUpdate(a));

context.SaveChanges();

This is what I expect from AssociatedProductsId Table:ID + ProductId (FK) + AssociatedProductsId(FK) + date + ......

But this is what I get:

What is my mistake ?Is this a good way to associate a product ?

解决方案

I think your classes are not right.

1 Problem: Why EF generates the table with extra columns?

In that case EF is using TPH strategy. Take a look at this link http://blogs.msdn.com/b/alexj/archive/2009/04/15/tip-12-choosing-an-inheritance-strategy.aspx

2 Problem: What is my mistake ? Is this a good way to associate a product ?

Your mapping should be something like this:

public class Product
{
    public int ProductId { get; set; }

    public string Name { get; set; }

    public virtual ICollection<ProductAssociation> AssociatedProducts { get; set; }

    public virtual ICollection<ProductAssociation> ProductsAssociatedThisProduct { get; set; }
}

public class ProductAssociation
{
    public int ProductId { get; set; }

    public int ProductAssociatedId { get; set; }

    public DateTime CreationDate { get; set; }

    public virtual Product Product { get; set; }

    public virtual Product ProductAssociated { get; set; }
}

public class Context : DbContext
{
    public Context() : base("Model2")
    {

    }

    public DbSet<Product> Products { get; set; }
    public DbSet<ProductAssociation> ProductsAssociations { get; set; }

    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        modelBuilder.Entity<Product>()
            .HasKey(i => i.ProductId);

        modelBuilder.Entity<ProductAssociation>()
            .HasKey(i => new {i.ProductId, i.ProductAssociatedId });

        modelBuilder.Entity<Product>()
            .HasMany(i => i.AssociatedProducts)
            .WithRequired(i => i.ProductAssociated)
            .HasForeignKey(i => i.ProductAssociatedId)
            .WillCascadeOnDelete(false);

        modelBuilder.Entity<Product>()
            .HasMany(i => i.ProductsAssociatedThisProduct)
            .WithRequired(i => i.Product)
            .HasForeignKey(i => i.ProductId)
            .WillCascadeOnDelete(false);


        base.OnModelCreating(modelBuilder);
    }


}

Seed

var product1 = new Product() { Name = "StarWars", ProductId = 1 };

var product2 = new Product() { Name = "StarWars II", ProductId = 2 };

context.ProductsAssociations.AddOrUpdate(new ProductAssociation { Product = product1, CreationDate = DateTime.Now, ProductAssociated = product2 });
context.Products.AddOrUpdate(product1);
context.Products.AddOrUpdate(product2);
context.SaveChanges();

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