调用 MVC 的目标已引发异常

Question

我有一个 ajax 调用，我需要从我的控制器中获取 JSON 格式的数据列表。我不断收到这个例外。

下面是我的 ajax 调用：

$('#button1').click(function (e) {
e.preventDefault();
var id= $("#textboxvalue").val();
debugger;
var url = "@Url.Action("GetList", "xyz")";
console.log(url);
$.ajax({
    url: url,
    type: "GET",
    async: false,
    data: { id: id},
    dataType: "json",
    traditional: true,
    contentType: "application/json; charset=utf-8",
    success: function (data) {
        debugger;
        for (var i in data) {       
        }
    },
    error: function (xhr, ajaxOptions, thrownError) {
        //Always goes to error function
        alert("An error has occured!!!");
    }
});
});

控制器代码：

我可以从ajax中获取参数值，从db中获取所有值。

    [HttpGet]
    public ActionResult GetList(string id)
    {

        var pList = new List<Property>();
        using (var db = new LiensTrackerEntities())
        {

            var recipient = db.Recipients.FirstOrDefault(x => x.id== id);
            //Need to make sure there is an Properties object
            if (recipient != null && 
recipient.RecipientPropertyCollections.Count() != 0)
            {
                List<int> properties = 
recipient.RecipientPropertyCollections.Select(p => p.Property_ID).ToList();

                foreach (var item in properties)
                {
                    Property p1 = db.Properties.FirstOrDefault(u => 
u.PropertyID == item);
                    pList.Add(p1);
                }
// I can see the values in pList on continue it goes to ERROR function in 
Ajax with 500 error
                return Json(pList, JsonRequestBehavior.AllowGet);
            }
        }
        return Json(" No spouse info in Medicaid", 
JsonRequestBehavior.AllowGet);
    }

异常信息：

调用的目标已抛出异常。

异常堆栈跟踪：

   at System.RuntimeMethodHandle.InvokeMethod(Object target, Object[] 
arguments, Signature sig, Boolean constructor)
   at System.Reflection.RuntimeMethodInfo.UnsafeInvokeInternal(Object obj, 
Object[] parameters, Object[] arguments)
   at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags 
invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
   at System.Web.SecurityUtils.MethodInfoInvoke(MethodInfo method, Object target, Object[] args)
   at System.Web.Script.Serialization.JavaScriptSerializer.SerializeCustomObject(Object o, StringBuilder sb, Int32 depth, Hashtable objectsInUse, SerializationFormat serializationFormat)
   at System.Web.Script.Serialization.JavaScriptSerializer.SerializeValueInternal(Object o, StringBuilder sb, Int32 depth, Hashtable objectsInUse, SerializationFormat serializationFormat, MemberInfo currentMember)
   at System.Web.Script.Serialization.JavaScriptSerializer.SerializeValue(Object o, StringBuilder sb, Int32 depth, Hashtable objectsInUse, SerializationFormat serializationFormat, MemberInfo currentMember)
   at System.Web.Script.Serialization.JavaScriptSerializer.SerializeEnumerable(IEnumerable enumerable, StringBuilder sb, Int32 depth, Hashtable objectsInUse, SerializationFormat serializationFormat)
   at System.Web.Script.Serialization.JavaScriptSerializer.SerializeValueInternal(Object o, StringBuilder sb, Int32 depth, Hashtable objectsInUse, SerializationFormat serializationFormat, MemberInfo currentMember)
   at System.Web.Script.Serialization.JavaScriptSerializer.SerializeValue(Object o, StringBuilder sb, Int32 depth, Hashtable objectsInUse, SerializationFormat serializationFormat, MemberInfo currentMember)
   at System.Web.Script.Serialization.JavaScriptSerializer.SerializeCustomObject(Object o, StringBuilder sb, Int32 depth, Hashtable objectsInUse, SerializationFormat serializationFormat)
   at System.Web.Script.Serialization.JavaScriptSerializer.SerializeValueInternal(Object o, StringBuilder sb, Int32 depth, Hashtable objectsInUse, SerializationFormat serializationFormat, MemberInfo currentMember)
   at System.Web.Script.Serialization.JavaScriptSerializer.SerializeValue(Object o, StringBuilder sb, Int32 depth, Hashtable objectsInUse, SerializationFormat serializationFormat, MemberInfo currentMember)
   at System.Web.Script.Serialization.JavaScriptSerializer.SerializeEnumerable(IEnumerable enumerable, StringBuilder sb, Int32 depth, Hashtable objectsInUse, SerializationFormat serializationFormat)
   at System.Web.Script.Serialization.JavaScriptSerializer.SerializeValueInternal(Object o, StringBuilder sb, Int32 depth, Hashtable objectsInUse, SerializationFormat serializationFormat, MemberInfo currentMember)
   at System.Web.Script.Serialization.JavaScriptSerializer.SerializeValue(Object o, StringBuilder sb, Int32 depth, Hashtable objectsInUse, SerializationFormat serializationFormat, MemberInfo currentMember)
   at System.Web.Script.Serialization.JavaScriptSerializer.Serialize(Object obj, StringBuilder output, SerializationFormat serializationFormat)
   at System.Web.Script.Serialization.JavaScriptSerializer.Serialize(Object obj, SerializationFormat serializationFormat)
   at System.Web.Script.Serialization.JavaScriptSerializer.Serialize(Object obj)
   at System.Web.Mvc.JsonResult.ExecuteResult(ControllerContext context)
   at System.Web.Mvc.ControllerActionInvoker.InvokeActionResult(ControllerContext controllerContext, ActionResult actionResult)
   at System.Web.Mvc.ControllerActionInvoker.InvokeActionResultFilterRecursive(IList`1 filters, Int32 filterIndex, ResultExecutingContext preContext, ControllerContext controllerContext, ActionResult actionResult)
   at System.Web.Mvc.ControllerActionInvoker.InvokeActionResultFilterRecursive(IList`1 filters, Int32 filterIndex, ResultExecutingContext preContext, ControllerContext controllerContext, ActionResult actionResult)
   at System.Web.Mvc.ControllerActionInvoker.InvokeActionResultWithFilters(ControllerContext controllerContext, IList`1 filters, ActionResult actionResult)
   at System.Web.Mvc.Async.AsyncControllerActionInvoker.<>c__DisplayClass21.<>c__DisplayClass2b.<BeginInvokeAction>b__1c()
   at System.Web.Mvc.Async.AsyncControllerActionInvoker.<>c__DisplayClass21.<BeginInvokeAction>b__1e(IAsyncResult asyncResult)

Answer 1

根据堆栈跟踪，当 MVC 尝试对返回值进行 JSON 序列化时，似乎发生了错误。由于此值为List<Property>，因此Property 类上可能有一个成员，该成员在某些情况下调用时会引发异常。

考虑创建一个单独的数据传输对象类来返回，而不是您正在使用的模型类。或者，检查 Entity 模型类，了解调用其属性可能引发异常的原因。

附带说明一下，如果您的实体模型设置正确，您应该能够大大简化查询逻辑：

    using (var db = new LiensTrackerEntities())
    {
        var pList = db.Properties
            .Where(p => p.RecipientPropertiesCollection
                .Any(rp => rp.RecipientId == id))
            .ToList();
        return Json(pList, JsonRequestBehavior.AllowGet);
    }

这将在一次数据库往返中完成，而您当前的代码会进行多次往返。