本文介绍了多对多映射表的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述 29岁程序员，3月因学历无情被辞！ 从我在网上看到的示例和编程实体框架CodeFirst的书中，当您有两个类的集合时，EF将创建一个映射表，如 MembersRecipes 和每个类的主键将链接到此表。 但是，当我执行以下操作时，我会在 Recipes 表$ code> Member_Id 和 Recipe_Id 在成员 table。 哪些只创建两个一对多的关系，但不是一对多的关系，所以我可以把会员3链接到食谱（ 4,5）和配方4链接到会员（1,2,3）等。 有没有办法创建这个映射表？如果是这样，你如何命名其他的东西，如cookbooks？ 谢谢 public abstract class Entity { [必需] public int Id {get;组; } public class成员：Entity { [必需] public string Name {get;组; } public virtual IList< Recipe>食谱{get;组; } public class配方：Entity { [必需] public string Name {get;组; } [ForeignKey（Author）] public int AuthorId {get;组; } public virtual Member作者{get;组; } .... public virtual IList< Member>会员{get;组; } 更新： 以下是另一种方法我已经尝试了不使用Fluent API并替换 AuthorId & 作者在食谱中拥有所有者标志，我也将以下示例从 Cookbooks 到 MembersRecipes ，这也解决了我的问题类似于答案，但是如上所述还有其他的影响。 [ForeignKey（Recipe）] [Key，Column（Order = 0） public int RecipeId {get;组; } public virtual配方食谱{get;组; [Key，Column（Order = 1）] [ForeignKey（Member）] public int MemberId {get;组; } public virtual Member Member {get;组; } public bool Owner {get;组; } } 和配方& 会员课程我将集合更改为 public virtual IList< MembersRecipes> MembersRecipes {get;组; 解决方案在DbContext OnModelCreating上执行此操作： protected override void OnModelCreating（DbModelBuilder modelBuilder） { modelBuilder.Entity< Recipe>（） .HasMany（x => x.Members） .WithMany（x => x.Recipes） .Map（x => { x.ToTable Cookbooks）; //第三个表命名为Cookbooks x.MapLeftKey（RecipeId）; x.MapRightKey（MemberId）; }）; } 你可以这样做，相同，只是另一个相同硬币的一边： modelBuilder.Entity< Member>（） .HasMany（x => x .Recipes） .WithMany（x => x.Members） .Map（x => { x.ToTable（Cookbooks）; //第三表名为Cookbooks x.MapLeftKey（MemberId）; x.MapRightKey（RecipeId）; }）; 其他示例： http://www.ienablemuch.com/2011/07/using-checkbox-list-on-aspnet-mvc-with_16.html http://www.ienablemuch.com/2011/07/nhibernate -equivalent-of-entity.html 更新 为了防止您的作者财产的周期性引用，除了上述之外，您需要添加以下内容： code> modelBuilder.Entity< Recipe>（） .HasRequired（x => x.Author） .WithMany（） .WillCascadeOnDelete（false）; 这里提供的想法： EF Code First with many to many self referenceing relationship 核心的是，您需要通知EF，作者属性（它是一个成员实例）没有配方集合（由 WithMany（）表示）;这样，可以在作者属性上停止循环引用。 这些是从上面代码第一个映射创建的表： $ b code $ c CREATE TABLE成员（ id int IDENTITY（1,1）NOT NULL主键，名称nvarchar（128）NOT NULL ） ; CREATE TABLE配方（ ID int IDENTITY（1,1）NOT NULL主键，名称nvarchar（128）NOT NULL， AuthorId int NOT NULL references成员（Id））; CREATE TABLE Cookbooks（ RecipeId int NOT NULL， MemberId int NOT NULL， constraint pk_Cookbooks主键（RecipeId，MemberId））; From examples that I have seen online and in a Programming Entity Framework CodeFirst book, when you have a collection on both classes EF would create a mapping table such as MembersRecipes and the primary key from each class would link to this table.However when I do the below, I instead get a new field in the Recipes table called Member_Id and a Recipe_Id in the Members table.Which only creates two one-to-many relationships, but not a many-to-many so I could have Member 3 linked to Recipes (4,5,6) and Recipe 4 linked to Members (1,2,3) etc.Is there a way to create this mapping table? and if so how do you name it something else such as "cookbooks" ?Thanks public abstract class Entity { [Required] public int Id { get; set; } } public class Member : Entity { [Required] public string Name { get; set; } public virtual IList<Recipe> Recipes { get; set; } } public class Recipe : Entity { [Required] public string Name { get; set; } [ForeignKey("Author")] public int AuthorId { get; set; } public virtual Member Author { get; set; } .... public virtual IList<Member> Members { get; set; } }UPDATE:Below is another approach I have tried which doesn't use the Fluent API and replaces the AuthorId & Author on Recipe with an owner flag, I have also renamed the below example from Cookbooks to MembersRecipes, this also fixes my issue similar to the answer but as mentioned has further implications.public class MembersRecipes { [Key, Column(Order = 0)] [ForeignKey("Recipe")] public int RecipeId { get; set; } public virtual Recipe Recipe { get; set; } [Key, Column(Order = 1)] [ForeignKey("Member")] public int MemberId { get; set; } public virtual Member Member { get; set; } public bool Owner { get; set; }}and in Recipe & Member classes I changed the collections topublic virtual IList<MembersRecipes> MembersRecipes { get; set; } 解决方案 Do this on your DbContext OnModelCreating:protected override void OnModelCreating(DbModelBuilder modelBuilder){ modelBuilder.Entity<Recipe>() .HasMany(x => x.Members) .WithMany(x => x.Recipes) .Map(x => { x.ToTable("Cookbooks"); // third table is named Cookbooks x.MapLeftKey("RecipeId"); x.MapRightKey("MemberId"); });}You can do it the other way around too, it's the same, just another side of the same coin:modelBuilder.Entity<Member>() .HasMany(x => x.Recipes) .WithMany(x => x.Members).Map(x =>{ x.ToTable("Cookbooks"); // third table is named Cookbooks x.MapLeftKey("MemberId"); x.MapRightKey("RecipeId");});Further examples:http://www.ienablemuch.com/2011/07/using-checkbox-list-on-aspnet-mvc-with_16.htmlhttp://www.ienablemuch.com/2011/07/nhibernate-equivalent-of-entity.htmlUPDATETo prevent cyclical reference on your Author property, aside from above, you need to add this:modelBuilder.Entity<Recipe>() .HasRequired(x => x.Author) .WithMany() .WillCascadeOnDelete(false);Idea sourced here: EF Code First with many to many self referencing relationshipThe core thing is, you need to inform EF that the Author property(which is a Member instance) has no Recipe collections(denoted by WithMany()); that way, cyclical reference could be stopped on Author property.These are the created tables from the Code First mappings above:CREATE TABLE Members( Id int IDENTITY(1,1) NOT NULL primary key, Name nvarchar(128) NOT NULL);CREATE TABLE Recipes( Id int IDENTITY(1,1) NOT NULL primary key, Name nvarchar(128) NOT NULL, AuthorId int NOT NULL references Members(Id));CREATE TABLE Cookbooks( RecipeId int NOT NULL, MemberId int NOT NULL, constraint pk_Cookbooks primary key(RecipeId,MemberId)); 这篇关于多对多映射表的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！ 上岸，阿里云！
