查看Foreach循環：ObjectContext實例已被處置，不能再用於需要連接的操作

Question

我正在用實體框架構建mvc Web應用程序。

錯誤：

An exception of type 'System.ObjectDisposedException' occurred in EntityFramework.dll but was not handled in user code

Additional information: The ObjectContext instance has been disposed and can no longer be used for operations that require a connection.

這是實體框架的一部分：

就像你看到的，我已經包括 「Alineas」，做.ToList（）

public IList<Kop> Handle(RetrieveKoppenForDocumentQuery query) 
     { 
      using (var db = new BmDataContext()) 
      { 
       var koppen = db.Kop.Where(s => s.Document.Id == query.Id) 
        .Include(s => s.TegelAfbeelding) 
        .Include(s => s.CollageAfbeeldingen) 
        .Include(s => s.FinancieleAfbeeldingen) 
        .Include(s => s.Alineas) 
        .ToList(); 
       return _orderKoppenByIndex(koppen); 
      } 
     } 

這是視圖KopListItems.cshtml：

@using PGE.Bestuursmonitor.Contracts.DataTypes 
@model IList<Kop> 

@* Helper for recursively rendering koppen*@ 
@helper SortableItem(Kop kop) 
{ 
    <div class="sortable-item" data-kopid="@kop.Id"> 
     <div class="row"> 
      <div class="col-md-7 title-column"> 
       <i class="fa fa-arrows"></i> @kop.Titel 
      </div> 
      <div class="col-md-5"> 
       <div class="col-md-3"> 
        <span> 
         @kop.KopType 
        </span> 
       </div> 
       <div class="col-md-3"> 
        <span> 
         @kop.Status 
        </span> 
       </div> 
       <div class="col-md-6"> 
        <span class="pull-right"> 
         @if (@kop.Alineas != null) // on this line I receive the exception 
         { 
          // here I would like to do some logic 
         } 
        </span> 
       </div> 
      </div> 
     </div> 
     <div class="sortable-container"> 
      @foreach (var subKop in kop.Koppen) 
      { 
       @SortableItem(subKop); 
      } 
     </div> 
    </div> 
} 


@* Recursively render all kop items *@ 
<div id="koppen_sortable" class="sortable-container"> 
    @foreach (Kop kop in Model) 
    { 
     @SortableItem(kop); 
    } 
</div> 

這是視圖KoppenList.cshtml：

@model PGE.Bestuursmonitor.ViewModels.Koppen.IKoppenListViewModel 

<h1>@Model.DocumentTitel</h1> 

@* Render kop list header *@ 
<div id="koppen_sortable_header"> 
    <div class="row"> 
     <div class="col-md-7"><strong>Titel</strong></div> 
     <div class="col-md-5"> 
      <div class="col-md-3"> 
       <strong>Type</strong> 
      </div> 
      <div class="col-md-3"> 
       <strong>Status</strong> 
      </div> 
      <div class="col-md-6"> 
       <span class="pull-right"> 
        <button type="button" id="btn_add_sub" class="btn btn-success" title="Kop aanmaken" role="button" onclick="BM.Koppen.LoadAddKopView(null);"> 
         <i class="fa fa-plus fa-lg"></i> Kop aanmaken 
        </button> 
       </span> 
      </div> 
     </div> 
    </div> 
</div> 
<div id="koppen_sortable_body"> 
    @{ Html.RenderPartial("~/Views/Koppen/KopListItems.cshtml", @Model.Koppen); } 
</div> 

@* Store document id in html DOM, so javascript can reach it from multiple places *@ 
<input type="hidden" id="document_id" value="@Model.DocumentId" /> 

動作控制器：

[HttpGet] 
     public ActionResult KoppenList(string id) 
     { 
      ViewBag.PageId = id; 

      Document document = _retrieveStartPcDocumentQueryHandler.Handle(new RetrieveStartPcDocumentQuery()); 

      RetrieveKoppenForDocumentQuery query = new RetrieveKoppenForDocumentQuery 
      { 
       Id = document.Id 
      }; 

      IList<Kop> koppen = _retrieveKoppenForDocumentQueryHandler.Handle(query); 

      _koppenListViewModel.Koppen = koppen; 
      _koppenListViewModel.DocumentTitel = document.Titel; 
      _koppenListViewModel.DocumentId = document.Id; 

      return View("~/Views/Koppen/KoppenList.cshtml", _koppenListViewModel); 
     } 

就像你在KopListItems.cshtml看到有2個foreach循環。外部的foreach循環工作正常，可以讀取「Alineas」。顯示子項目的內部foreach給出了這個奇怪的錯誤。出了什麼問題？我卡住了。

Answer 1

這是解決方案。你需要得到alineas和內容也分等級：

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