Entity Framework 中的外键错误

Question

我正在计划一个简单的两个table结构：

1）老师Table：

public class TeacherAccount
{
    [DataType(DataType.Text), Required()]
    public string Name { get; set; }

    [DataType(DataType.Text), Required()]
    public string Address { get; set; }

    [DataType(DataType.EmailAddress), Required(), Key]
    public string Email { get; set; }

    [DataType(DataType.Password), Required()]
    public string Password { get; set; }

    [DataType(DataType.Password), Compare("Password"), Required(), NotMapped]
    public string ConfirmPassword { get; set; }

    public bool Activated { get; set; }

}

2) 老师教授的科目：

public class Teacher_Subject_Map
{
    [ForeignKey("TeacherAccount")]
    public string Email { get; set; }
    public string Subjects;
}

我的理念是：识别老师的email，可以有多个科目，是那个老师教的。

我是怎么得到这个的：

The ForeignKeyAttribute on property 'Email' on type 'xpertsdesk.Models.Teacher_Subject_Map' is not valid. The navigation property 'TeacherAccount' was not found on the dependent type 'xpertsdesk.Models.Teacher_Subject_Map'. The Name value should be a valid navigation property name.

作为 mvc5 中的错误。

我正在尝试做什么：

Create table Teacher(Email varchar(30) Primary Key, Other Details);
Create table Subjects(Email varchar(30) References Teacher(Email), Subject varchar(30));

我做错了什么？

Answer 1

如果一个科目只能由一位老师教授（一对多关系）：
在这种情况下，不会有映射 table.

public class Subject
{
    [Key]
    public string Name { get; set; }

    // This will hold the Key of Teacher
    public string TeacherEmail { get; set; }

    [ForeignKey("TeacherEmail")]
    public virtual Teacher Teacher { get; set; }
}

public class Teacher
{
    /* the original properties comes here, e.g. Email */
    public string Email { get; set; }

    // Navigation property for taught subjects
    public virtual ICollection<Subject> Subjects { get; set; }
}

如果一个学科可以由更多的老师教授（多对多关系）：
Subject class 就是这样。

public class Subject
{
    [Key]
    public string Name { get; set; }

    /* other properties if needed */

    public virtual ICollection<Teacher> Teachers { get; set; }
}

然后可以在自己的DbContext中配置多对多关系class:

protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
    modelBuilder
        .Entity<Teacher>()
        .HasMany(teacher => teacher.Subjects)
        .WithMany(subject => subject.Teachers)
        .Map(c =>
        {
            c.ToTable("Teacher_Subject_Map");
            c.MapLeftKey("TeacherEmail");
            c.MapRightKey("SubjectName");
        });
}

Entity Framework 中的外键错误

ForeignKey error in Entity Framework

c#

entity-framework-5

asp.net-mvc-5