C# 500内部服务器错误JsonResult mvc asp.net
试图用jsonresult和ajax创建一个级联下拉菜单,但我不明白为什么会出现500个内部服务器错误。错误发生在以下方法之上:C# 500内部服务器错误JsonResult mvc asp.net,c#,json,ajax,asp.net-mvc,C#,Json,Ajax,Asp.net Mvc,试图用jsonresult和ajax创建一个级联下拉菜单,但我不明白为什么会出现500个内部服务器错误。错误发生在以下方法之上: [HttpGet] public JsonResult GetModels(string brandID="") { List<Model> models = new List<Model>(); int ID = 0; if (int.TryParse(brandID,
[HttpGet]
public JsonResult GetModels(string brandID="")
{
List<Model> models = new List<Model>();
int ID = 0;
if (int.TryParse(brandID, out ID))
{
using (CarsEntities1 dc = new CarsEntities1())
{
models = dc.Models.Where(a => a.Brand_ID == ID).OrderBy(a =>a.Model_name).ToList();
}
}
if (Request.IsAjaxRequest())
{
return new JsonResult
{
Data = models,
JsonRequestBehavior = JsonRequestBehavior.AllowGet
};
}
else
{
return new JsonResult
{
Data = "Not valid request",
JsonRequestBehavior = JsonRequestBehavior.AllowGet
};
}
}
我使用该方法将项目列表传递到下拉菜单中,并尝试通过以下代码输出列表:
$(document).ready(function () {
//if (typeof ($) == 'function') alert('jQuery is loaded.');
$("#brand_Brand_ID").change(function () {
// this will call when Brand Dropdown select change
var brandID = parseInt($("#brand_Brand_ID").val());
if (!isNaN(brandID)) {
var ddModel = $("#Model_ID");
ddModel.empty(); // this line is for clear all items from Model dropdown
ddModel.append($("<option></option").val("").html("Select model"));
// Here I will call Controller Action via Jquery to load Model for selected Brand
$.ajax({
url: "@Url.Action("GetModels","ModelSpec")",
type: "GET",
data: { brandID: brandID },
dataType: "json",
success: function (data) {
if (data != null && data.success) {
$.each(data, function (i, val) {
ddModel.append(
$("<option></option>").val(val.Model_ID).html(val.Model_name)
);
});
}
},
error: function () {
alert("Fail");
}
});
}
});
});
我得到的只是以下信息:
获取500内部服务器错误jquery-1.7.1.js行8102
我还注意到,当没有数据通过GetModels方法时,不会发生错误。有时我会:
GET/ModelSpec/GetModels?brandID=5
一旦GetModels返回任何内容,就会发生错误,否则不会发生
ObjectContext实例已被释放,无法再用于
需要连接的操作
堆栈跟踪:
您需要将return语句移动到using块中 在执行return语句之前,将释放Db上下文
public JsonResult GetModels(int brandID)
{
List<Model> models = new List<Model>();
using (CarsEntities1 dc = new CarsEntities1())
{
models = dc.Models.Where(a => a.Brand_ID == brandID).OrderBy(a =>a.Model_name);
if (Request.IsAjaxRequest())
{
return new JsonResult
{
Data = models.ToList(),
JsonRequestBehavior = JsonRequestBehavior.AllowGet
};
}
}
return new JsonResult
{
Data = "Not valid request",
JsonRequestBehavior = JsonRequestBehavior.AllowGet
};
}
json返回类型必须是原语,因此我将code accordinglyswap List更改为String[],并将OrderBy更改为选择:
public JsonResult GetModels(int brandID)
{
String[] models;
using (CarsEntities1 dc = new CarsEntities1())
{
models = dc.Models.Where(a => a.Brand_ID == brandID).Select(a=> a.Model_name).toArray();
if (Request.IsAjaxRequest())
{
return new JsonResult
{
Data = models,
JsonRequestBehavior = JsonRequestBehavior.AllowGet
};
}
}
return new JsonResult
{
Data = "Not valid request",
JsonRequestBehavior = JsonRequestBehavior.AllowGet
};
}
你能粘贴错误描述吗?它将在错误回调中可用,甚至可以使用开发工具。此外,您可以在操作中放置断点以查看失败的位置。您可以将方法声明中的字符串brandID=替换为int brandID。然后可以删除此控件:int.TryParsebrandID,out ID。它可能会解决问题,但可能不会。你能试一试吗?试过了,但没什么变化。