如何在EF Core中添加父实体和2级子实体，同时更新1级子实体？

// 定义实体类
public class ParentEntity
{
    public int Id { get; set; }
    public string Name { get; set; }
    public ICollection<Level1Entity> Level1Entities { get; set; }
}

public class Level1Entity
{
    public int Id { get; set; }
    public string Name { get; set; }
    public int ParentEntityId { get; set; }
    public ParentEntity ParentEntity { get; set; }
    public ICollection<Level2Entity> Level2Entities { get; set; }
}

public class Level2Entity
{
    public int Id { get; set; }
    public string Name { get; set; }
    public int Level1EntityId { get; set; }
    public Level1Entity Level1Entity { get; set; }
}

// 创建上下文
public class MyDbContext : DbContext
{
    public DbSet<ParentEntity> ParentEntities { get; set; }
    public DbSet<Level1Entity> Level1Entities { get; set; }
    public DbSet<Level2Entity> Level2Entities { get; set; }

    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
    {
        optionsBuilder.UseSqlServer("your_connection_string");
    }

    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        modelBuilder.Entity<Level1Entity>()
            .HasOne(e => e.ParentEntity)
            .WithMany(p => p.Level1Entities)
            .HasForeignKey(e => e.ParentEntityId);

        modelBuilder.Entity<Level2Entity>()
            .HasOne(e => e.Level1Entity)
            .WithMany(l => l.Level2Entities)
            .HasForeignKey(e => e.Level1EntityId);
    }
}

// 添加父实体和1级子实体，同时更新1级子实体
using (var context = new MyDbContext())
{
    var parentEntity = new ParentEntity { Name = "Parent" };
    var level1Entity = new Level1Entity { Name = "Level 1", ParentEntity = parentEntity };
    var level2Entity = new Level2Entity { Name = "Level 2", Level1Entity = level1Entity };

    context.ParentEntities.Add(parentEntity);
    context.Level1Entities.Add(level1Entity);
    context.Level2Entities.Add(level2Entity);

    level1Entity.Name = "Updated Level 1";
    context.Update(level1Entity);

    context.SaveChanges();
}