为什么实体框架仅保存列表的最后一项? [英] why does entity framework saves only the last item of a list?

问题描述

我有2个具有一对多关系的对象.我试图在使用通用存储库的同时将多个具有相同ProductId的ProductImage添加到数据库中.

I have 2 objects with one to many relation. I'm trying to add multiple ProductImages with the same ProductId to the data base, while using a generic repository.

我尝试使用dbSet.AddRange将ProductImage列表保存到存储库中.之后，我用context.SaveChanges();保存了它.我也尝试过遍历ProductImage列表，并使用dbSet.Add添加每个项目，而不是context.SaveChanges().

I have tried saving a list of ProductImage to a repository with dbSet.AddRange . after that i saved it with context.SaveChanges(); i have also tried looping trough the list of ProductImage and adding each item with dbSet.Add .and than context.SaveChanges() .

存储库方法:

    public virtual void Add(TEntity entity)
        {
            dbSet.Add(entity);
        }

        public virtual void AddRange(List<TEntity> entityList)
        {
            dbSet.AddRange(entityList);
        }
        public void Save()
        {
            context.SaveChanges();
    }

结果是保存到数据库的对象始终是最后一个-但我想保存所有对象.

the result is the object saved to the data base is always the last one - but i want to save all of them.

修改添加对象的方法:

        private  Task<int> InsertProductImagesToDB(List<ProductImageVM> productImages, int productId, List<IFormFile> imageFiles)
        {
            if (productImages?.Any()==true)
            {
                List<ProductImage> dbEntitys = new List<ProductImage>();
                for(int i=0; i< productImages.Count; i++)
                {
                    ProductImage p = productImages[i].ConvertToProductImageEntity(imageFiles[i], productId);
                    dbEntitys.Add(p);
                }
                ImagesRepository.AddRange(dbEntitys);
                ImagesRepository.Save();
                return Task.FromResult(dbEntitys.First().Id);//return first productImage as the main image
            }
            return Task.FromResult(-1);
        }

正如您在注释中提到的那样-对象构造函数不在循环之外.调试时，我可以看到dbEntitys列表包含2个具有不同值的项目.

as some of you mentioned in the comments - the object constructor is not outside the loop. while debugging i can see the dbEntitys list contains 2 items with defferent values.

图像:保存更改后的数据库表:

image of the dbset after adding the objects before saving changes: db table after changes were saved:

推荐答案

将我的头撞在墙上几天后-我终于找到了解决方案.

after banging my head against the wall for a few days - i finally got the solution.

问题出在我的ProductImage实体中，如下所示:

the problem was in my ProductImage Entity which looked like this:

   public class ProductImage : ImageProp, DBEntity
    {
        [Column("Name", TypeName = "nvarchar(200)"), Required, Display(Name = "שם"), MaxLength(200)]
        public string Name { get; set; }

        public Product Product { get; set; } 

        [Required]
        public int ProductId { get; set; }

    }

所以问题出在这一行:

  public Product Product { get; set; } 

显然为数据库表中的ProductId字段创建了唯一键.当我尝试添加具有相同ProductId的多个ProductImage时，出现了一个SQL异常，提示我无法为ProductId插入重复值.

which apparently created a unique key for ProductId field in the data base table. when i tried to add multiple ProductImages with the same ProductId, i got an sql exception that said i cannot insert duplicate value for ProductId.

删除此行解决了问题.

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