首先使用實體​​框架代碼刪除關系

Question

我已經使用Entity Framework Code First和最新的Entity Framework版本創建了自己的數據庫模型。

我有這個課：

[DataContract]
public class User
{
    [DataMember]
    public int UserId { get; set; }

    [DataMember]
    public string Name { get; set; }

    [DataMember]
    public int Age { get; set; }

    [DataMember]
    public string City { get; set; }

    [DataMember]
    public string Country { get; set; }

    [DataMember]
    public string Email { get; set; }

    [DataMember]
    public string InterestIn { get; set; }


    [DataMember]
    public virtual ICollection<User> Friends { get; set; }

    [DataMember]
    public virtual ICollection<User> FromWhomIsFriend { get; set; }

    [DataMember]
    public virtual ICollection<Activity> WantsToDo { get; set; }

    [DataMember]
    public virtual ICollection<Message> MessagesSent { get; set; }

    [DataMember]
    public virtual ICollection<Message> MessagesReceived { get; set; }

    public override string ToString()
    {
        string output = string.Empty;

        output = String.Format("UserId: {0}, Name: {1}, Age: {2}, City: {3}, " +
            "Country: {4}, Email: {5}, InterestIn: {6}",
            UserId, Name, Age, City, Country, Email, InterestIn);

        return output;
    }
}

及其配置類：

class UserConfiguration : EntityTypeConfiguration<User>
{
    public UserConfiguration()
    {
        Property(d => d.Name).IsRequired();
        Property(d => d.Age).IsRequired();
        Property(d => d.City).IsRequired();
        Property(d => d.Country).IsRequired();
        Property(d => d.Email).IsRequired();
        Property(d => d.InterestIn).IsRequired();

        HasMany(d => d.MessagesSent).WithRequired(l => l.SentByUser).WillCascadeOnDelete(false);
        HasMany(d => d.MessagesReceived).WithRequired(l => l.SentToUser).WillCascadeOnDelete(false);

        HasMany(d => d.Friends).
            WithMany(d => d.FromWhomIsFriend).
            Map(c =>
                {
                    c.ToTable("UserFriends");
                    c.MapLeftKey("UserId");
                    c.MapRightKey("FriendId");
                });
        HasMany(d => d.WantsToDo).
            WithMany(a => a.Users).
            Map(t =>
                {
                    t.ToTable("UserActivities");
                    t.MapLeftKey("UserId");
                    t.MapRightKey("ActivityId");
                });
    }
}

代表這種多對多的自我關系：

現在我有一個問題：我不知道如何刪除朋友關系。 使用SQL，我將執行以下操作：

DELETE FROM UserFriend
WHERE (userId = user1_id   AND friendId = friend1_id) OR
      (userId = friend1_id AND friendId = user1_id)

user1_id ：是要刪除朋友關系的用戶。 friend1_id ：是user1要刪除的朋友。

我該怎么做？

Answer 1

只需從集合中刪除朋友：

user.Friends.Remove(friendToRemove);

Answer 2

因此，如果我沒有正確理解，如果用戶User1與User2是朋友，則該關系將位於user1.Friends或user1.FromWhomIsFriend 。

您應該檢查關系在哪里，並相應地將其刪除。

 public void RemoveFriend(User user, User friend)
 {
   if (user1.Friends.Contains(friend));
      user1.Friends.Remove(friend);
   if (user1.FromWhomIsFriend.Contains(friend));
      user1.FromWhomIsFriend.Remove(friend);
 }