Question

有人可以解释为什么Entity Framework不会在连接表中创建额外的列CurVal和NewVal吗？它正在创建一个包含DeviceFeatureID和UserDeviceID的联接表。

public class DeviceFeature
{
        [Display(Name = "ID")]
        public int DeviceFeatureID { get; set; }

        [Required]        
        public string Name { get; set; }
        public string Description { get; set; }

        public virtual ICollection<DeviceType> DeviceTypes { get; set; }
        public virtual ICollection<UserDevice> UserDevices { get; set; }
}

public class UserDevice
{
        public int UserDeviceID { get; set; }
        public int DeviceTypeID { get; set; }
        public string UserID { get; set; }
        public string DeviceName { get; set;}

        public virtual ICollection<DeviceFeature> DeviceFeatures { get; set; }
}

public class UserDeviceFeatureStatus
{
        public int UserDeviceID { get; set; }
        public int DeviceFeatureID { get; set; }

        public virtual UserDevice UserDevice { get; set; }
        public virtual DeviceFeature DeviceFeature { get; set; }

        public string CurVal { get; set; }
        public string NewVal { get; set; }
}

Answer 1

您的多对多关系表由您的虚拟馆藏自动生成，而不是由您的实体生成。

您可以在DbContext中包含连接实体（但它可能会复制表，除非您删除虚拟集合），或者您可以使用Fluent API来配置关系。

要执行稍后操作，您需要将虚拟馆藏更改为ReleationShip类型并将其添加到OnModelCreating：

  modelBuilder.Entity<UserDeviceFeatureStatus>()
        .HasKey(t => new { t.UserDeviceID, t.DeviceFeatureID });

    modelBuilder.Entity<UserDeviceFeatureStatus>()
        .HasOne(pt => pt.UserDevice)
        .WithMany(p => p.DeviceFeatures) // from UserDevice
        .HasForeignKey(pt => pt.UserDeviceID);

    modelBuilder.Entity<UserDeviceFeatureStatus>()
        .HasOne(pt => pt.DeviceFeature)
        .WithMany(t => t.UserDevices) //from DeviceFeature
        .HasForeignKey(pt => pt.DeviceFeatureID);

在DeviceFeature中

public virtual ICollection<UserDeviceFeatureStatus> UserDevices { get; set; }

在UserDevice中

public virtual ICollection<UserDeviceFeatureStatus> DeviceFeatures { get; set; }

有关EF关系的详细信息，您可以查看文档here。

Answer 2

如果您想在UserDevice和DeviceFeature到UserDeviceFeatureStatus之间建立多对多关系，那么您需要将2个表格中的导航属性设置为＆＃34 ;加入＆＃34;表。我们了解到，您尝试直接从UserDevice导航到DeviceFeature，反之亦然。但如果您的关系表包含的其他字段不是您尝试链接的表格的主键，那么您将无法在EF中执行此操作。

你可以试试这个：

public class DeviceFeature
{
    [Display(Name = "ID")]
    public int DeviceFeatureID { get; set; }

    [Required]        
    public string Name { get; set; }
    public string Description { get; set; }

    public virtual ICollection<DeviceType> DeviceTypes { get; set; }
    public virtual ICollection<UserDeviceFeatureStatus> UserDeviceFeatureStatuses { get; set; }

}

public class UserDevice
{
    public int UserDeviceID { get; set; }
    public int DeviceTypeID { get; set; }
    public string UserID { get; set; }
    public string DeviceName { get; set;}

    public virtual ICollection<UserDeviceFeatureStatus> UserDeviceFeatureStatuses { get; set; }
}

public class UserDeviceFeatureStatus
{

    public int UserDeviceID { get; set; }
    public int DeviceFeatureID { get; set; }

    public virtual UserDevice UserDevice { get; set; }
    public virtual DeviceFeature DeviceFeature { get; set; }

    public string CurVal { get; set; }
    public string NewVal { get; set; }
}

例如，要从UserDevice导航到DeviceFeature，您需要先导航到UserDeviceFeatureStatus然后再导航到DeviceFeature。

实体框架不在连接表中创建额外的列

2 个答案: