如何从 EF Core 中的父实体中删除子实体？

Question

我有这些 class

public class HomeSection2
{
    public HomeSection2()
    {
        HomeSection2Detail = new List<HomeSection2Detail>();
    }

    public Guid ID { get; set; }
    public string Title { get; set; }
    public string Header { get; set; }

    public virtual List<HomeSection2Detail> HomeSection2Detail { get; set; }
}

public class HomeSection2Detail
{
    public Guid ID { get; set; }
    public string Title { get; set; }
    public string Description { get; set; }
    public string Link { get; set; }
    public int? Sequence { get; set; }

    public virtual HomeSection2 HomeSection2 { get; set; }
}

当我打电话给

var obj2detail = obj2.HomeSection2Detail.Where(w => w.ID == detail.ID).FirstOrDefault();
if (obj2detail != null)
{
    obj2.HomeSection2Detail.Remove(obj2detail);
}  

在我的应用程序中，它只会删除关系而不是数据库中的记录。

Answer 1

您需要执行以下操作。在代码段中添加为评论的解释：

var obj2detail = obj2.HomeSection2Detail.Where(w => w.ID == detail.ID).FirstOrDefault();
if (obj2detail != null)
{
    // this line of code only delete the relationship.
    obj2.HomeSection2Detail.Remove(obj2detail);

    // If you want to delete the entity you need the DbContext help 
    // and your HomeSection2Details DbSet<HomeSection2Detail> like below
    yourDbContext.HomeSection2Details.Remove(obj2detail);
}

Answer 2

您需要从 HomeSection2Details DbSet 中明确删除实体。

dbContext.HomeSection2Details.Remove(obj2detail);

Answer 3

您直接使用 RemoveRange 或 Remove DbContext

 _db.RemoveRange(obj2detail);

Answer 4

无需从 DbContext 中显式删除依赖实体；如果依赖实体在从其主体实体中删除时应该 总是 被删除，这可以通过 DbContext 上的配置来实现，使用 OnDelete:

protected override void OnModelCreating(ModelBuilder builder)
{
    builder
        .Entity<HomeSection2>()
        .HasMany(x => x.HomeSection2Detail)
        .WithOne(x => x.HomeSection2)
        .OnDelete(DeleteBehavior.Cascade); // Causes dependent entity to be deleted
}