用json和實體框架填充下拉列表

Question

我想通過ajax調用填充下拉列表我的代碼工作正常，直到我發回JSON格式的結果（對象列表）。

這是我試圖填補我的實體模型：

public partial class stkInvoicesTypesTbl 
{ 
    [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Usage", "CA2214:DoNotCallOverridableMethodsInConstructors")] 
    public stkInvoicesTypesTbl() 
    { 
     this.stkInvoicesTbls = new HashSet<stkInvoicesTbl>(); 
    } 

    public int invTypesTableId { get; set; } 
    public string invTypeDesc { get; set; } 

    [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Usage", "CA2227:CollectionPropertiesShouldBeReadOnly")] 
    public virtual ICollection<stkInvoicesTbl> stkInvoicesTbls { get; set; } //this property throw Exception and i think here is my problem 
} 

這裏是我的ajax調用和腳本代碼

var InvType = [] 

// fetch invoice type from database 
function LoadInvoiceType(element) 
{ 
    if (InvType.length == 0) { 
     //ajax function to fetch data 
     $.ajax({ 
      type: "GET", 
      url: '/InvoiceItm/getInvoiceType', 

      success: function (data) { 
       InvType = data; 

       renderInvoiceType(element); 
      }, 
      error: function (data) { 
       InvType = data; 
      } 
     }) 
    } 
    else { 
     //render invoice type to elements 
     renderInvoiceType(element); 
    } 
} 

function renderInvoiceType(element) 
{ 
    var $ele = $(element); 
    $ele.empty(); 

    $.each(InvType, function (i, val) { 
     $ele.append($('<option/>').val(val.invTypesTableId).text(val.invTypeDesc)); 
    }) 
} 

我的動作控制器：

public JsonResult getInvoiceType() 
{ 
     List<stkInvoicesTypesTbl> InvoiceTypes = new List<stkInvoicesTypesTbl>(); 

     using (iraqEntities dc = new iraqEntities()) 
     { 
      InvoiceTypes = dc.stkInvoicesTypesTbls.OrderBy(a => a.invTypeDesc).ToList(); 
     } 

     return new JsonResult { Data = InvoiceTypes, JsonRequestBehavior = JsonRequestBehavior.AllowGet }; 
} 

我查看：

<td><label for="input-text" class="col-sm-1 control-label">Invoice Type</label> </td> 
      <td> 
       <select type="text" id="InvoiceType" class="col-sm-3 form-control" onchange="LoadInvoiceType(this)"></select> 

      </td> 

我的列表在控制器中正確填寫，但是當我以json格式發回（返回JsonResult ...）時，它返回錯誤。

這裏是一些截圖爲我調試可能會有所幫助：

return my data from database and fill my list in controller

this property is generated automatically from Entity Framework (foreign key relation) and it's throwing an exception so I think my problem lies here

所以，任何人都可以幫助我在我的問題是可以理解的

Answer 1

你需要在查詢中包含屬性stkInvoicesTbls

using (iraqEntities dc = new iraqEntities()) 
    { 
     InvoiceTypes = dc.stkInvoicesTypesTbls 
         .Include("stkInvoicesTbls") 
         .OrderBy(a => a.invTypeDesc) 
         .ToList(); 
    }