[英]How to create a third table for Many to Many relationship in Entity Framework Core?
我有兩節課:一是用戶
public class User
{
public int Id { get; set; }
public string FirstName { get; set; }
public string LastName { get; set; }
public string Email { get; set; }
public List<Subscription> Subscriptions { get; set; }
}
其他是訂閱:
public class Subscription
{
public int Id { get; set; }
public string Name { get; set; }
public decimal Price { get; set; }
}
如您所見,該用戶具有訂閱列表。 現在,當使用實體框架代碼第一種方法時,我將獲得一個用戶表,該表不包含訂閱,但是將用戶ID的新列添加到訂閱表中。 我期望有第三個表,其中包含兩列,一列具有用戶ID,另一列具有訂閱ID。 我該如何實現?
創建第三個中間表,例如: UserSubscriptions
。
public class User
{
public int ID { get; set; }
public string FirstName { get; set; }
public string LastName { get; set; }
public string Email { get; set; }
public virtual ICollection<UserSubscription> Subscriptions { get; set; }
}
public class Subscription
{
public int ID { get; set; }
public string Name { get; set; }
public decimal Price { get; set; }
}
public class UserSubscription
{
public int ID { get; set; }
public int SubscriptionID { get; set; }
public decimal Price { get; set; }
public int UserID { get; set; }
public virtual User { get; set; }
public DateTime BeginDate { get; set; }
public DateTime EndDate { get; set; }
}
第二種解決方案:
例如,將Subscription
引用添加到User
並將其命名為CurrentSubscription
。
public class User
{
public int ID { get; set; }
public string FirstName { get; set; }
public string LastName { get; set; }
public string Email { get; set; }
public int CurrentSubscriptionID { get; set; }
public virtual Subscription Subscription { get; set; }
}
public class Subscription
{
public int ID { get; set; }
public string Name { get; set; }
public decimal Price { get; set; }
}
從文檔 :
尚不支持沒有實體類來表示聯接表的多對多關系。 但是,可以通過為聯接表包括一個實體類並映射兩個單獨的一對多關系來表示多對多關系。
所以這個答案是正確的。
我只是更正了一點代碼:
class MyContext : DbContext
{
public DbSet<Use> Users { get; set; }
public DbSet<Subscription> Subscriptions { get; set; }
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
modelBuilder.Entity<UserSubscription>()
.HasKey(t => new { t.UserId, t.SubscriptionId });
modelBuilder.Entity<UserSubscription>()
.HasOne(pt => pt.User)
.WithMany(p => p.UserSubscription)
.HasForeignKey(pt => pt.UserId);
modelBuilder.Entity<UserSubscription>()
.HasOne(pt => pt.Subscription)
.WithMany(t => t.UserSubscription)
.HasForeignKey(pt => pt.SubscriptionId);
}
}
public class User
{
public int Id { get; set; }
public string FirstName { get; set; }
public string LastName { get; set; }
public string Email { get; set; }
public List<UserSubscription> UserSubscriptions{ get; set; }
}
public class Subscription
{
public int Id { get; set; }
public string Name { get; set; }
public decimal Price { get; set; }
public List<UserSubscription> UserSubscriptions{ get; set; }
}
public class UserSubscription
{
public int UserId { get; set; }
public User User { get; set; }
public int SubscriptionId { get; set; }
public Subscription Subscription { get; set; }
}
PS。 您無需在導航屬性中使用virtual,因為在EF Core中仍然無法進行延遲加載。
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