Question

我在两个类之间创建了多对多关系。

public class Member
{
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public Guid MemberId { get; set; }
    public string Name { get; set; }

    public virtual ICollection<Group> Groups { get; set; } 

    public Member()
    {
        Groups = new HashSet<Group>();
    }
}

public class Group
{
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public Guid GroupId { get; set; }
    public string Name { get; set; }

    public virtual ICollection<Member> Members { get; set; } 

    public Group()
    {
        Members = new HashSet<Member>();
    }
}

protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
    modelBuilder.Entity<Group>().HasMany(x => x.Members).WithMany(c => c.Groups)
        .Map(y =>
                 {
                     y.MapLeftKey("GroupId");
                     y.MapRightKey("MemberId");
                     y.ToTable("Group_to_Member");
                 });
}

如果我测试它，这是有效的：

var member = new Member();
member.Name = "Smith";
db.Members.Add(member);

var group = new Group();
group.Name = "Group 1";
db.Groups.Add(group);

member.Groups.Add(group);
group.Members.Add(member);

db.SaveChanges();

但是如何删除组中的成员？我试过这个： var group = db.Groups.First（）; db.Groups.Remove（基）; db.SaveChanges（）;

我只是不断得到“DELETE语句与REFERENCE约束冲突”。那么我怎么能告诉它先删除关联然后再输入？

Answer 1

请参阅RedHat关于将数据库中的FK设置为在删除时级联的注释。

EF 4.2 Code首先，如何删除多对多关联？

1 个答案: