Question

好吧，这可能是一个我错了的概念，但无论如何...... （MVC3）我有一个带有list属性的实体。我的CRUD视图通过Ajax帖子向控制器发送JSon表示。一切都很好，除了当我发布该实体的更新时，list属性根本没有更新。实体的所有简单属性都会更新，但（正如我想象的）更新树不包括List属性。如何让EF了解列表中的这些更改？

到目前为止，这是一些代码：

    [HttpPost]
    public JsonResult Edit(Lote lote)
    {
            //Given the IDs present in lote.Documentos, load the List of Documentos
            if (lote.Documentos != null)
            {
                List<Documento> ldoc = new List<Documento>();
                foreach (var d in lote.Documentos)
                {
                    ldoc.Add(db.Documentos.Find(d.IDDocumento));
                }
                lote.Documentos.Clear();
                foreach (var d in ldoc)
                {
                    lote.Documentos.Add(d);
                }
            }

            //Now, clear all the previous errors
            foreach (var modelValue in ModelState.Values)
            {
                modelValue.Errors.Clear();
            }
            //And re-validate the model
            ValidateModel(lote);

            if (ModelState.IsValid)
            {
                if (lote.IDLote > 0)
                {
                    //Updating
                    db.Entry(lote).State = EntityState.Modified;
                }
                else
                {
                    //Inserting
                    db.Lotes.Add(lote);
                }
                db.SaveChanges();
                CustomMessages.Sucesso(TempData, "Informações salvas com sucesso.", 10000);
                return Json(new { Success = 1, IDProprietario = lote.IDLote, ex = "" });
            }
            else
            {
                return Json(new { Success = 0, ex = "Falha na rotina de armazenamento das informações"});
            }

这些都是班级本身：

public class Lote
{
    [Key]
    public int IDLote { get; set; }

    (... lots of properties ...)

    [Display(Name = "Documentos")]
    public List<Documento> Documentos { get; set; }
}


public class Documento
{
    //---=== ATRIBUTOS ===---
    [Key]
    public int IDDocumento { get; set; }

    [Required]
    [MaxLength(60)]
    public string Nome { get; set; }

    public List<Lote> Lotes { get; set; }
}

由于这是一个多对多的关系，我也得到了这个：

    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        modelBuilder.Conventions.Remove
        <System.Data.Entity.ModelConfiguration.Conventions.PluralizingTableNameConvention>();

        modelBuilder.Entity<Lote>()
            .HasMany(t => t.Documentos)
            .WithMany(t => t.Lotes)
            .Map(m =>
            {
                m.ToTable("LoteDocumento");
                m.MapLeftKey("IDLote");
                m.MapRightKey("IDDocumento");
            });
(... and some other stuff)

对此有何帮助？

Answer 1

尝试更改此行：

ldoc.Add(db.Documentos.Find(d.IDDocumento));

到

ldoc.Add(db.Documentos.Include("Lotes").FirstOrDefault(x => x.IDDocumento == d.IDDocumento));

您需要确保您要更改的关系/对象实际上已附加到当前的DB上下文中。否则，实体框架将无法跟踪对它们所做的更改。

This link explains it in terms of object context, but I think the same rules apply to DBcontext.

如果这不起作用，请告诉我因为我真的想要更好地理解EF的工作方式。

好的，找到了一些有用的链接：

An object with the same key already exists in the ObjectStateManager. The ObjectStateManager cannot track multiple objects with the same key

Entity Framework and Connection Pooling

执行Include("Lotes")时，会将与Documentos相关的抽奖添加到DBContext。实体框架现在正在跟踪这些对象。在您的代码中，您将使用此行db.Entry(lote).State = EntityState.Modified;将其重新添加到上下文中。无论如何，这是我的猜测。

根据上面的链接，我会尝试重新编写你喜欢的内容（未编译）：

[HttpPost]
public JsonResult Edit(Lote lote)
{
    //get old Lote from DB
    var oldLote = db.Lotes.include("Documentos").FirstOrDefault(x => x.IDLote == lote.IDLote);

    //update
    if(oldLote != null)
    {
        //refresh any other properties that you may have changed on it.
        db.Entry(oldLote).CurrentValues.SetValues(lote);

        //not sure if you will even need this section any more but then you can...
        oldLote.Documentos.Clear();
        foreach (var d in lote.Documentos)
        {
            oldLote.Documentos.Add(db.Documentos.include("Lotes").FirstOrDefault(x => x.IDDocumento == d.IDDocumento));
        }
    }    
    else //add
    {
        //not sure if this will work
        foreach (var d in lote.Documentos)
        {
            db.Entry(d).State = EntityState.Modified;
        }

        db.Lotes.Add(lote);
    }

    //then just save changes.  EF is already tracking all your objects and changes.
    db.SaveChanges();
....

列表属性未由EF更新

1 个答案: