许多一对多映射表 [英] Many-to-many mapping table
问题描述
这是我所看到的在网上和一个编程实体框架codeFirst书，当你有两个类EF将创建一个映射表，如 MembersRecipes 并从每个类的主键将链接到该表中。
然而，当我做下面，我反而获得 Member_Id 名为食谱表和一个新的领域 Recipe_Id 在成员表。
其中仅创建了两个一到多的关系，而不是多到很多，所以我可以有会员3挂食谱（4,5,6）和配方4链接到会员（1,2,3 ）等。
有没有一种方法来创建这个映射表？如果是这样，你如何将其命名为别的东西，如食谱？
感谢
公共抽象类实体{
[需要]
公众诠释标识{搞定;组; }
} 公共类会员：实体{
[需要]
公共字符串名称{;组; } 公共虚拟的IList＆LT;＆配方GT;食谱{搞定;组; }
} 公共类方药：实体{
[需要]
公共字符串名称{;组; } [ForeignKey的（作者）]
公众诠释AUTHORID {搞定;组; }
公共虚拟会员作者{搞定;组; } .... 公共虚拟的IList＆LT;＆成员GT;成员{搞定;组; }
}
更新：
下面是另一种方法我都试过不使用流利的API，并替换 AUTHORID ＆安培; 作者在食谱与所有者标志，我也改名为从食谱下面的例子到 MembersRecipes ，这也解决类似的回答我的问题，但提到有进一步的影响。
公共类MembersRecipes { [键，列（订单= 0）]
[ForeignKey的（配方）]
公众诠释RecipeId {搞定;组; }
公共虚拟配方配方{搞定;组; } [键，列（订单= 1）]
[ForeignKey的（会员）]
公众诠释MEMBERID {搞定;组; }
公共虚拟会员会员{搞定;组; } 公共BOOL所有者获得{;组; }
}
和食谱＆安培; 成员类，我改变了馆藏
public虚拟的IList＆LT; MembersRecipes＆GT; MembersRecipes {搞定;组; }
做到这一点对你的DbContext OnModelCreating：
保护覆盖无效OnModelCreating（DbModelBuilder模型构建器）
{
modelBuilder.Entity＆LT;＆配方GT;（）
.HasMany（X =＆GT; x.Members）
.WithMany（X =＆GT; x.Recipes）
.MAP（X =＆GT;
{
x.ToTable（食谱）; //第三个表名为食谱
x.MapLeftKey（RecipeId）;
x.MapRightKey（MEMBERID）;
}）;
}
您可以做它的其他方式太身边，这是同一枚硬币的一样，只是另一面：
modelBuilder.Entity＆LT;＆成员GT;（）
.HasMany（X =＆GT; x.Recipes）
.WithMany（X =＆GT; x.Members）
.MAP（X =＆GT;
{
x.ToTable（食谱）; //第三个表名为食谱
x.MapLeftKey（MEMBERID）;
x.MapRightKey（RecipeId）;
}）;
进一步的例子：
<一个href=\"http://www.ienablemuch.com/2011/07/using-checkbox-list-on-aspnet-mvc-with_16.html\">http://www.ienablemuch.com/2011/07/using-checkbox-list-on-aspnet-mvc-with_16.html
<一个href=\"http://www.ienablemuch.com/2011/07/nhibernate-equivalent-of-entity.html\">http://www.ienablemuch.com/2011/07/nhibernate-equivalent-of-entity.html
更新
要在你的Author属性prevent循环引用，除了上面，你需要补充一点：
modelBuilder.Entity＆LT;＆配方GT;（）
.HasRequired（X =＆GT; x.Author）
.WithMany（）
.WillCascadeOnDelete（假）;
在这里采购的理念：<一href=\"http://stackoverflow.com/questions/5273569/ef-$c$c-first-with-many-to-many-self-referencing-relationship\">EF code先用多对多的自我引用关系
核心的事情是，你需要告知EF的Author属性（这是一个成员实例）没有处方集（由 WithMany表示为（））;这样一来，循环参考可以停在Author属性。
以上是从code以上第一映射创建表：
CREATE TABLE成员（
ID INT IDENTITY（1,1）NOT NULL主键，
名称为nvarchar（128）NOT NULL
）;
CREATE TABLE食谱（
ID INT IDENTITY（1,1）NOT NULL主键，
名称为nvarchar（128）NOT NULL，
AUTHORID诠释NOT NULL引用成员（ID）
）;
CREATE TABLE食谱（
RecipeId诠释NOT NULL，
MEMBERID诠释NOT NULL，
约束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 to
public virtual IList<MembersRecipes> MembersRecipes { get; set; }
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.html
http://www.ienablemuch.com/2011/07/nhibernate-equivalent-of-entity.html
UPDATE
To 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 relationship
The 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)
);
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