如何从 EF Core 中的父实体中删除子项？

Question

我有这些课

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

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

从我的应用程序中，它只会删除关系而不是数据库中的记录。

Answer 1

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

dbContext.HomeSection2Details.Remove(obj2detail);

Answer 2

您需要执行以下操作。 在代码段中作为注释添加的解释：

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 3

无需从DbContext显式删除依赖实体； 如果从其主体实体中删除依赖实体时应始终删除它，则可以通过使用OnDelete在DbContext上进行配置来实现：

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
}

Answer 4

您直接从 RemoveRange 或 Remove DbContext 使用

 _db.RemoveRange(obj2detail);