c# – 如何将两个不同的对象插入数据库,但检查它们是否已经存在

情况草图

我开发了一个系统,其中可以将许多材料(代码为Matetiaal)添加到广告中(在代码Zoeker中).这种关系很多很多.在这里你得到了我的课程结构.

+-------------------------------------+   many to many   +-------------------------------+
|                Zoeker               | <--------------> |           Materiaal           |
+------------+------------------------+                  +---------+---------------------+
| ID         | int                    |                  | ID      | int                 |
| Materialen | ICollection<Materiaal> |                  | Zoekers | ICollection<Zoeker> |
| Titel      | string                 |                  | Naam    | string              |
+------------+------------------------+                  +---------+---------------------+

我将使用下一个伪代码添加新材料和广告：

void Insert(Zoeker zoeker,string[] materialen) 
{
    foreach (string m in materialen)
    {
        Materiaal mat = materiaalRepo.GetByName(m);

        if (mat == null)
        {
            mat = materiaalRepo.Insert(new Materiaal(m));
        }

        zoeker.Materialen.Add(mat);
    }

    zoekerRepo.Insert(zoeker);
}

换句话说,当必须添加新广告(Zoeker)时,我将检查数据库中是否已存在该材料.如果材料不存在,则materialenRepo.GetByName(string)方法返回null.如果是这样,请将新材质插入数据库并返回Materiaal对象.之后或者如果materialenRepo.GetByName(string)没有返回null,请将该材料添加到广告的Materialen属性并将其插入数据库.

要将数据库与我的应用程序连接,我使用Entity Framework.

我的问题

当我在下面的标题上使用代码时,我有这个例外：

System.InvalidOperationException: An entity object cannot be referenced by multiple instances of IEntityChangeTracker.

06002

当zoekerRepo.Insert(zoeker)时,在标记的行上抛出异常;叫做.

我的代码

在这里你可以找到我制作的代码.

服务

public class ZoekService
{
    public int InsertZoeker(Zoeker zoeker,ApplicationUser user,string materialenString)
    {
        return InsertZoeker(zoeker,user,materialenString.Split(','));
    }

    public int InsertZoeker(Zoeker zoeker,string[] materialen)
    {
        zoeker.Gebruiker = user;
        zoeker.Materialen = new List<Materiaal>();

        using (ApplicationDbContext ctx = new ApplicationDbContext())
        {
            ZoekerRepository zoekerRepo = new ZoekerRepository(ctx);
            MateriaalRepository materiaalRepo = new MateriaalRepository(ctx); 
            // ^^^^ See update one

            foreach (string m in materialen)
            {
                Materiaal materiaal = materiaalRepo.GetByNaam(m);

                if (materiaal == null)
                {
                    materiaal = materiaalRepo.Insert(new Materiaal(m)); 
                    // ^ See update three
                }

                zoeker.Materialen.Add(materiaal);
            }

            zoekerRepo.Insert(zoeker); 
            zoekerRepo.SaveChanges(); // <-- Pointer didn't come on this line.

            return zoeker.ID;
        }
    }
}

库

ZoekerRepository扩展了GenericRepository< Zoeker>

public class ZoekerRepository : GenericRepository<Zoeker>
{
    public ZoekerRepository()
    { }

    public ZoekerRepository(ApplicationDbContext ctx): base(ctx)
    { }

    // Some other methods I've add or will override.
}

MateriaalRepository扩展了GenericRepository< Materiaal>

public class MateriaalRepository : GenericRepository<Materiaal>
{
    public MateriaalRepository()
    { }

    public MateriaalRepository(ApplicationDbContext ctx): base(ctx)
    { }

    public Materiaal GetByNaam(string naam)
    {
        return (from m in dbSet
                where m.Naam.Equals(naam)
                select m).SingleOrDefault<Materiaal>();
    }

    // Some other methods I've add or will override.
}

GenericRepository< TEntity>

public class GenericRepo<TEntity> where TEntity : class
{ 
    internal ApplicationDbContext context;
    internal DbSet<TEntity> dbSet;

    public GenericRepo()
    {
        context = new ApplicationDbContext();
        dbSet = context.Set<TEntity>();
    }

    public GenericRepo(ApplicationDbContext context)
    {
        this.context = context;
        this.dbSet = context.Set<TEntity>();
    }

    public virtual TEntity Insert(TEntity entity)
    {
        return dbSet.Add(entity); // <-- after `zoekerRepo.Insert(Zoeker)` the exception
                                  //       will be thrown on this line.
    }

    public void SaveChanges()
    {
        try
        {
            context.SaveChanges();
        }
        catch (Exception ex)
        {
            Console.WriteLine(ex.Message);
        }
    }
}

我做了什么

当然我已经尝试了其他代码,但所有代码都给出了相同的异常.我将创建我的代码,以便材料的存储库使用名为GenericRepo< TEntity>的相同通用类与广告存储库中的存储库分隔. (除了我要添加或覆盖的东西).我将尽可能多地重用它.一次用于GenericRepo< Zoeker>和GenericRepo< Materiaal>的另一个时间.

我的问题

我怎么能解决这个bug？

更新一个

这个问题与entity object cannot be referenced by multiple instances of IEntityChangeTracker. while adding related objects to entity in Entity Framework 4.1不重复,因为我使用相同的上下文,如接受的答案说：

You can fix this by creating a context outside of the service classes and injecting and using it in both services:

06007

请参阅上面代码的评论.

更新两个

在这里,我已经完成了我的代码的新部分.

控制器

public class DeelController : Controller
{
    private UserManager<ApplicationUser> UserManager { get; set; }
    private ZoekService _zoekservice = new ZoekService();

    public DeelController()
    {
        this.UserManager = new UserManager<ApplicationUser>(new UserStore<ApplicationUser>(ApplicationDbContext));
    }

    [HttpGet]
    [Authorize]
    public ActionResult Nieuw()
    {
        return View(new Zoeker());
    }

    [HttpPost]
    [Authorize]
    [ValidateAntiForgeryToken]
    public async Task<ActionResult> Nieuw(Zoeker zoeker)
    {
        _zoekservice.InsertZoeker(zoeker,await UserManager.FindByNameAsync(User.Identity.Name),zoeker.MaterialenString);

        return RedirectToAction(nameof(Index));
    }
}

类

Zoeker扩展了Post

public class Zoeker: Post
{
    public virtual ICollection<Materiaal> Materialen { get; set; }
    public virtual ICollection<ApplicationUser> Delers { get; set; }

    [NotMapped]
    public string MaterialenString { get; set; } // <-- contains a comma separated
                                                 //       list of all materials
}

岗位

public class Post
{
    [Key]
    public int ID { get; set; }
    public string Titel { get; set; }
    public string Omschrijving { get; set; }
    public virtual ApplicationUser Gebruiker { get; set; }
    public string GebruikerID { get; set; }
    public DateTime StartPeriode { get; set; }
    public DateTime? Verwijderd { get; private set; }
    public DateTime? Opgelost { get; private set; }
    public DateTime? Belangerijk { get; private set; }
    public virtual ICollection<Antwoord> Antwoorden { get; set; }
}

更新三

我也尝试使用此代码替换上面代码中的注释行,但没有解决此错误：

materiaal = /*materiaalRepo.Insert(*/ new Materiaal(m); //);

如果我使用不存在的材料,使用更新三的代码,我再次遇到了这个错误.

更新四

如果我使用观察者,我会看到：

Material [0]得到了一个字段_entityWrapper类型的EntityWrapperWithoutRelationships< System.Data.Entity.DynamicProxies.Materiaal_E0DDEFDA63D33C75C64324662B40FDC414EC19CA4AD6BF18443B63FC60015374>.注意：此材料已存在于数据库中.在这里我也有同样的错误.

更新五

我也取代了`InsertZoeker(Zoeker

public int InsertZoeker(Zoeker zoeker,string[] materialen)
{
    Zoeker newZoeker = new Zoeker()
    {
        Gebruiker = user,StartPeriode = DateTime.Now,Materialen = new List<Materiaal>(),Titel = zoeker.Titel,Omschrijving = zoeker.Omschrijving
    };

    using (ApplicationDbContext ctx = new ApplicationDbContext())
    {
        ZoekerRepository zoekerRepo = new ZoekerRepository(ctx);
        MateriaalRepository materiaalRepo = new MateriaalRepository(ctx);

        foreach (string m in materialen)
        {
            Materiaal materiaal = materiaalRepo.GetMateriaalByNaam(m);

            if (materiaal == null)
            {
                materiaal = /*materiaalRepo.Insert(*/ new Materiaal(m); //);
            }

            newZoeker.Materialen.Add(materiaal);
        }

        zoekerRepo.Insert(newZoeker);
        zoekerRepo.SaveChanges();

        return zoeker.ID;
    }
}