许多一对多使用EF code首先关系 [英] Many-to-many relationships using EF Code First

问题描述

我有两个类定义是这样的：

I have two classes defined as such:

public class Questionnaire
    {
        public int QuestionnaireID { get; set; }
        public string Title { get; set; }
        public bool Active { get; set; }
        public virtual ICollection<Question> Questions { get; set; }
        public virtual ICollection<Vendor> Vendors { get; set; }
    }

public class Vendor
    {
        public int VendorID { get; set; }

        public string VendorName { get; set; }

        public virtual ICollection<Questionnaire> OpenQuestionnaires { get; set; }

        public virtual ICollection<Questionnaire> SubmittedQuestionnaires { get; set; }

        public virtual ICollection<QuestionnaireUser> QuestionnaireUsers { get; set; }
    }

我beleive这是建立这些类之间的许多一对多的关系，正确的方法，并且在该项目建成后，我会希望创​​建三个表。

I beleive this is the correct way to establish a many-to-many relationship between these classes, and when the project is built, I would expect three tables to be created.

然而，当我试图以涉及一份问卷，以两个不同的供应商，我收到试图保存更改时出现以下错误（context.SaveChanges（））：

However, when I attempt to to relate one Questionnaire to two different Vendors, I receive the following error when attempting to save the changes (context.SaveChanges()):

*违反了多重限制。关系QuestionnaireApp.Models.Vendor_OpenQuestionnaires'的作用Vendor_OpenQuestionnaires_Source具有多重1或0..1。*

*Multiplicity constraint violated. The role 'Vendor_OpenQuestionnaires_Source' of the relationship 'QuestionnaireApp.Models.Vendor_OpenQuestionnaires' has multiplicity 1 or 0..1.*

如果我给你一份调查问卷，只有一个卖方，保存更改，然后将其分配到另一个，并再次保存更改我不再得到的错误;然而该问卷随后只与最后卖方它被指定，这表明（充其量）有正在创建一对多的关系。

If I assign a Questionnaire to only one Vendor, save the changes and then assign it to another and again save changes I no longer get the error; however the Questionaire is then related only to the last Vendor to which it was assigned, indicating that (at best) there is a one-to-many relationship being created.

我希望有什么毛病我声明了这些类之间的许多一对多的关系的方式，或者是有一些我需要添加上下文类鼓励的relationsip，但不支持这样也许很多一对多的关系，否则不能使用code首先被创造的？

I'm hoping that there is something wrong with the way I'm declaring the many-to-many relationship between these classes, or perhaps there is something I need to add to the context class to "encourage" the relationsip, but perhaps many-to-many relationships like this are not supported, or cannot be created using "Code First"?

感谢您的时间，

杰森

推荐答案

去图，经过一个小时左右的搜索，我去找到确切答案，30秒后我张贴我的问题。

Go figure, after an hour or so of searching, I go and find the exact answer 30 seconds after I post my question.

解决的办法是添加以下上下文类：

The solution was to add the following to the context class:

modelBuilder.Entity<Vendor>()
                .HasMany<Questionnaire>(x => x.OpenQuestionnaires)
                .WithMany(x => x.Vendors)
                .Map(x =>
                    {
                        x.MapLeftKey("vID");
                        x.MapRightKey("qID");
                        x.ToTable("VendorQuestionnaires");
                    });

我找到了答案通过阅读这个堆栈溢出职位：的 EF code首先许多到许多不工作

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