Entity framework 实体框架代码第一个映射(链接)表?
我正在使用EF代码优先的方法,希望添加一个链接(映射)表。我正在处理以下示例,并得到以下错误:Entity framework 实体框架代码第一个映射(链接)表?,entity-framework,entity-framework-4,entity-framework-4.1,Entity Framework,Entity Framework 4,Entity Framework 4.1,我正在使用EF代码优先的方法,希望添加一个链接(映射)表。我正在处理以下示例,并得到以下错误: System.Data.Entity.Edm.EdmEntityType: : EntityType 'EmployeeDepartmentLink' has no key defined. Define the key for this EntityType. 问题是我不想在这个表上有一个键它只是将两个表映射在一起: public class Employee { [Key()]
System.Data.Entity.Edm.EdmEntityType: : EntityType 'EmployeeDepartmentLink' has no key defined. Define the key for this EntityType.
问题是我不想在这个表上有一个键它只是将两个表映射在一起:
public class Employee
{
[Key()]
public int EmployeeID;
public string Name;
}
public class Department
{
[Key()]
public int DepartmentID;
public string Name;
}
public class EmployeeDepartmentLink
{
public int EmployeeID;
public int DepartmentID;
}
我尝试过各种方法,比如添加“[Key()]”属性,但使用它没有意义,我应该将它添加到哪个字段?我想知道是否支持这种表模型?对于
M:M关系
您必须创建您的join(link)类,如下所示
public class EmployeeDepartmentLink
{
[Key, Column(Order = 0)]
public int EmployeeID;
[Key, Column(Order = 1)]
public int DepartmentID;
}
有关更多信息,请查看
我希望这将对您有所帮助。您正在尝试进行“多对多”映射
要执行此操作,请编写以下代码:
public class Employee
{
[Key]
public int EmployeeId;
public string Name;
public List<Department> Departments { get; set; }
public Employee()
{
this.Departments = new List<Department>();
}
}
public class Department
{
[Key]
public int DepartmentId;
public string Name;
public List<Employee> Employees { get; set; }
public Department()
{
this.Employees = new List<Employee>();
}
}
检查这正是我要找的@user1882453很高兴听到这有帮助!我知道,在fluentapi中,不创建第三个对象来表示映射表是可能的。
public class YourContext : DbContext
{
public DbSet<Employee> Employees { get; set; }
public DbSet<Department> Departments { get; set; }
public YourContext() : base("MyDb")
{
}
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
modelBuilder.Entity<Department>().
HasMany(c => c.Employees).
WithMany(p => p.Departments).
Map(
m =>
{
m.MapLeftKey("DepartmentId");
m.MapRightKey("EmployeeId");
m.ToTable("DepartmentEmployees");
});
}
}