C# Entity Framework 6 - AutoMapper 6 - Collections/List - 添加和更新有效但删除项目会引发错误

Question

正如标题所说，我可以添加和更新，但是在删除时出现错误。

The operation failed: The relationship could not be changed because one or more of the foreign-key properties is non-nullable. When a change is made to a relationship, the related foreign-key property is set to a null value. If the foreign-key does not support null values, a new relationship must be defined, the foreign-key property must be assigned another non-null value, or the unrelated object must be deleted.

我知道在这种情况下 Description 只会得到一个空外键，但永远不会被删除。我见过一些例子，他们建议循环遍历每个 child 项目并一个一个地删除它们。 Imao 我认为应该有更好的方法。我正在寻找的是一个影响最小的解决方案，只需告诉 EF 删除整个项目，而不仅仅是将外键设为 null。

使用 AutoMapper，AutoMapper.Collection 和 AutoMapper.Collection。EntityFramework。

控制器方法：

public async Task<IHttpActionResult> UpdateArticle(ArticleViewModel articleVm)
{
    Article articleOriginal = await iArticleRepository.GetAsync(articleVm.Id);
    Article updatedArticle = Mapper.Map<ArticleViewModel, Article>(articleVm, articleOriginal);
    await iArticleRepository.UpdateAsync(updatedArticle);
    return Ok();
}

映射：

Mapper.Initialize(cfg =>
{
    cfg.AddCollectionMappers();

    cfg.SetGeneratePropertyMaps<GenerateEntityFrameworkPrimaryKeyPropertyMaps<DbContext>>();

    cfg.CreateMap<ArticleViewModel, Article>(MemberList.Source)
        .EqualityComparison((src, dst) => src.Id == dst.Id);

    cfg.CreateMap<DescriptionViewModel, Description>(MemberList.Source)
        .EqualityComparison((src, dst) => src.Id == dst.Id);
}
Mapper.AssertConfigurationIsValid();

视图模型：

public class ArticleViewModel
{
    public int Id { get; set; }

    public string Name { get; set; }

    public List<DescriptionViewModel> Descriptions { get; set; }
}

public class DescriptionViewModel
{
    public int Id { get; set; }

    public string Heading { get; set; }
}

型号：

public class Article : IEntity<int>
{
    public Article()
    {
        Descriptions = new List<Description>();
    }

    [Key]
    public int Id { get; set; }

    public DateTime Created { get; set; }

    public DateTime Updated { get; set; }

    [MaxLength(256)]
    public string Name { get; set; }

    public virtual ICollection<Description> Descriptions { get; set; }
}

public class Description: IEntity<int>
{
    [Key]
    public int Id { get; set; }

    public DateTime Created { get; set; }

    public DateTime Updated { get; set; }

    [MaxLength(256)]
    public string Heading { get; set; }

    public int ArticleId { get; set; }

    public virtual Article Article { get; set; }
}

Answer 1

从这个答案中得到了解决方案

和这个博客：

http://www.kianryan.co.uk/2013/03/orphaned-child/

代码：

public class Description: IEntity<int>
{
    [Key, Column(Order = 0), DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public int Id { get; set; }

    public DateTime Created { get; set; }

    public DateTime Updated { get; set; }

    [MaxLength(256)]
    public string Heading { get; set; }

    [Key, Column(Order = 1)]
    public int ArticleId { get; set; }

    public virtual Article Article { get; set; }
}

我真的可以推荐阅读 Mosh's answer 了解 composition 和 aggregation 之间的区别，因为它将帮助您更好地理解 EF .

C# Entity Framework 6 - AutoMapper 6 - Collections/List - 添加和更新有效但删除项目会引发错误

C# Entity Framework 6 - AutoMapper 6 - Collections/List - Add and Update works but removing item throws an error

c#

entity-framework

automapper

entity-framework-6

automapper-6