Entity Framework 代码优先以意外方式生成 tables/keys

Question

我有很多类表，但有三个让我头疼：Person、Task 和 Role，这是它们的代码：

public class Person : BaseModel
{
        public int Id { get; set; }
        public string FName { get; set; }
        public string LName { get; set; }
        public string Title { get; set; }

        public ICollection<TestEvent> TestEventsLed { get; set; }
        public ICollection<TestEvent> TestEventsCreated { get; set; }
        public ICollection<Program> ProgramsLed { get; set; }
        public ICollection<Task> TasksCreated { get; set; }
        public ICollection<PersonalEvent> PersonalEventsCreated { get; set; }

        public virtual ICollection<Role> RolesHeld { get; set; }
        public virtual ICollection<Task> TasksAssigned { get; set; }
}

public class Role : BaseModel
{
        public int Id { get; set; }
        public string Name { get; set; }

        public virtual ICollection<Person> PeopleWithThisRole { get; set; }
}

public class Task : BaseModel
{
        public int Id { get; set; }
        public string Name { get; set; }
        public DateTime SuspenseDatetime { get; set; }
        public DateTime CreatedDatetime { get; set; }
        public int CreatedById { get; set; }
        public bool Completed { get; set; }
        public bool Archived { get; set; }

        public Person CreatedBy { get; set; }

        public virtual ICollection<Person> PeopleAssigned { get; set; }
}

我最终得到的大部分是我想要的，除了一些小问题：

Expected:                                       Actual:
- People should have 0 foreign keys, just       - People has 1 FK and 1 extra column out of
  2 many-to-manys for RolesHeld and               nowhere: Task_Id and the FK is for that
  TasksAssigned                                   new column referencing Id in Tasks?

- Task should have 1 foreign key for            - Task has 2 extra columns out of nowhere
  CreatedById linked to a Person                  called Person_Id and Person_Id1 and then
                                                  identical foreign keys attached to them
                                                  (and it has the expected CreatedById FK)

- There should be a RolePersons table           - This part happened correctly and with the 
  with 2 FKs to represent the many-to-many        correct FKs to represent the many-to-many

- There should be a TaskPersons table           - There is no new table at all for this
  with 2 FKs to represent the many-to-many

奇怪的是，我以相同的方式做了其中一些（比如两个多对多关系），但只有 1 个结果是正确的？你能看出我做错了什么吗？

Answer 1

Entity Framework按惯例做事。

查看您的任务 class 和人员 class

public class Task : BaseModel
{
    public int Id { get; set; }
    public string Name { get; set; }
    public DateTime SuspenseDatetime { get; set; }
    public DateTime CreatedDatetime { get; set; }
    public int CreatedById { get; set; }
    public bool Completed { get; set; }
    public bool Archived { get; set; }

    public Person CreatedBy { get; set; }

    public virtual ICollection<Person> PeopleAssigned { get; set; }
}


public class Person : BaseModel
{
    public int Id { get; set; }
    public string FName { get; set; }
    public string LName { get; set; }
    public string Title { get; set; }

    public ICollection<TestEvent> TestEventsLed { get; set; }
    public ICollection<TestEvent> TestEventsCreated { get; set; }
    public ICollection<Program> ProgramsLed { get; set; }
    public ICollection<Task> TasksCreated { get; set; }
    public ICollection<PersonalEvent> PersonalEventsCreated { get; set; }

    public virtual ICollection<Role> RolesHeld { get; set; }
    public virtual ICollection<Task> TasksAssigned { get; set; }
}

在您的任务 Class 中，您正在放置 Person 对象以及 Person.That 的集合，我猜这就是让您头疼的原因。

如果你需要它们之间的多对多关系，那么你不应该把这个属性放在你的任务中 Class

 public Person CreatedById { get; set; }
 public Person CreatedBy { get; set; }

或者如果您需要它们之间的一对多关系，则从您的任务中删除此属性 class

 public virtual ICollection<Person> PeopleAssigned { get; set; }

Answer 2

有时默认映射不是我们想要的，所以我们必须明确地告诉 EF 我们需要什么。只需将此方法添加到您的 DbContext 中，它就会按要求工作：

protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
    modelBuilder.Entity<Person>().HasMany(p => p.TasksAssigned).WithMany(t => t.PeopleAssigned);
    modelBuilder.Entity<Person>().HasMany(p => p.TasksCreated).WithRequired(t => t.CreatedBy).WillCascadeOnDelete(false);
}

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