Question

我必须复制一组recodrs并将它们添加到带有新ID的数据库中。

var subEntities= ct.SubEntities.Where(qf => qf.ParentEntityId == oldParentEntityId).ToList();
subEntities.ForEach(qf => { qf.ParentEntityId = newParentEntityId; qf.Id = default(int); });
ct.SubEntities.AddRange(subEntities);

当AddRange运行时，所有实体subEntities都有令人尴尬的ID，如-2147482647，虽然有正确的序列，但它们会进入db。如何解决？

我的实体类和映射：

public class SubEntity
{
    public int Id { get; set; }
    public Guid ParentEntityId { get; set; }
    public virtual ParentEntity ParentEntity { get; set; }
    //props
}

public class ParentEntity 
{
    public Guid Id { get; set; }
    public virtual List<SubEntity> SubEntities { get; set; }
    //props
}

//OnModelCreating
builder.Entity<ParentEntity>()
    .HasMany(q => q.SubEntities)
    .WithOne(qf => qf.ParentEntity)
    .HasForeignKey(qf => qf.ParentEntityId)
    .OnDelete(Microsoft.EntityFrameworkCore.Metadata.DeleteBehavior.Cascade);

Answer 1

问题在于提取ParentEntity的方式。它被EF跟踪（我也认为SubEntities也是如此），所以我尝试添加一个已被跟踪的集合。我不太了解EF在这种情况下的工作方式，但解决方案是：

var subEntities= ct.SubEntities
    .Where(qf => qf.ParentEntityId == oldParentEntityId)
    .AsNoTracking()
    .ToList();

Npgsql AddRange索引上的EF Core

1 个答案: