用json和实体框架填充下拉列表

Question

我想通过ajax调用填充下拉列表我的代码工作正常，直到我发回JSON格式的结果（对象列表）。

这是我试图填补我的实体模型：

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 
} 

这里是我的ajax调用和脚本代码

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)); 
    }) 
} 

我的动作控制器：

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确填写，但是当我以json格式发回（返回JsonResult ...）时，它返回错误。

这里是一些截图为我调试可能会有所帮助：

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，任何人都可以帮助我在我的问题是可以理解的

Answer 1

你需要在查询中包含属性stkInvoicesTbls

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