我在View中有一个AJAX调用，它很难从数据库拉到填充下拉列表。数据库已填充。在浏览器控制台中我可以看到它找到了正确的ID，但是我收到以下错误：
"Failed to load resource: the server responded with a status of 500 (Internal Server Error)"
点击此链接将我带到服务器错误：
"The parameters dictionary contains a null entry for parameter 'serviceId' of non-nullable type 'System.Int32' for method 'System.Web.Mvc.JsonResult GetServiceDetails(Int32)' in 'YardLad.Controllers.ServiceController'. An optional parameter must be a reference type, a nullable type, or be declared as an optional parameter. Parameter name: parameters"
这是我到目前为止的代码：
AJAX致电：
function GetServices() {
$.ajax({
type: "GET",
url: "/Service/GetServices",
data: { serviceAreaId: $('#ServiceAreaId').val() },
datatype: 'JSONP',
async: true
})
.done(function (services) {
$('#ServiceId').empty(); //commenting this line gets the field to never populate with nulls, leaving the
//"loading services..." there permanently, also brings up the request a contractor button.
$.each(services, function (i, service) { //the i is the index being passed to it... service is the value
$("#ServiceId").append(
$('<option/>')
.attr('value', this.ServiceId)
.text(this.Name)
);
});
GetServiceDescription();
});
}
控制器：
//
// GET: Service/GetServices/
public JsonResult GetServices(int serviceAreaId)
{
// selected service area
var selectedServiceArea = db.ServiceAreas.Where(sa => sa.ServiceAreaId == serviceAreaId).SingleOrDefault();
var currentDate = DateTime.Now.AddHours(2);
// list of contractors that are listed (and not expired) and have at least one contractor service added
var contractors = db.Contractors.Where(c => c.IsActive == true).Where(c => c.ExpiresOn.Value >= currentDate).Where(c => c.ContractorServices.Count >= 1).ToList();
HashSet<int> contractorIds = new HashSet<int>(contractors.Select(x => x.ContractorId));
// filter list of contractors to include only those who offer services in the selected service area
var primary = db.Contractors.ToList().FindAll(x => contractorIds.Contains(x.ContractorId))
.Where(c => c.ServiceAreaId == serviceAreaId).Distinct().ToList();
var secondary = db.ContractorServiceAreas.ToList().FindAll(x => contractorIds.Contains(x.ContractorId))
.Where(csa => csa.ServiceAreaId == serviceAreaId).Select(x => x.Contractor).Distinct().ToList();
foreach (var contractor in secondary)
{
if (primary.Contains(contractor) == false)
{
primary.Add(contractor);
}
}
// only return services in the selected service area that contractors have added
HashSet<int> filteredContractorIds = new HashSet<int>(primary.Select(x => x.ContractorId));
var services = db.ContractorServices.ToList().FindAll(x => filteredContractorIds.Contains(x.ContractorId))
.Select(x => x.Service).Distinct().OrderBy(s => s.ServiceCategory.Name).ThenBy(s => s.Name)
.Select(x => new {
ServiceId = x.ServiceId,
Name = x.Name
});
return this.Json(services, JsonRequestBehavior.AllowGet);
}
//
// GET: Service/GetServiceDetails/1
public JsonResult GetServiceDetails(int serviceId)
{
var details = db.Services.Where(s => s.ServiceId == serviceId)
.Select(x => new
{
Description = x.Description,
BasePrice = x.BasePrice
});
return this.Json(details, JsonRequestBehavior.AllowGet);
}
.cshtml
@using (Html.BeginForm("RequestService", "Service", FormMethod.Post))
{
<div class="two-third" style="margin-right: 0;">
<div id="requestService" style="overflow: auto">
<h2>Request a Service</h2>
@Html.ValidationSummary(true)
<div class="display-label">Select a State</div>
<div class="editor-field">
<select id="StateId" name="StateId">
<option value="0">loading states...</option>
</select>
</div>
<div class="display-label">Select a Service Area</div>
<div class="editor-field">
<select id="ServiceAreaId" name="ServiceAreaId">
<option value="0">loading service areas...</option>
</select>
</div>
<div class="display-label">Select a Service</div>
<div class="editor-field">
<select id="ServiceId" name="ServiceId">
<option value="0">loading services...</option>
</select>
</div>
<div class="selectedService" style="display: none;">
<div class="display-label">Service Description</div>
<div class="editor-field" id="ServiceDescription"></div>
<div class="serviceOptions" id="ServiceOptions"></div>
<div style="text-align: right;">
<input type="submit" id="SubmitRequest" value="Select a Contractor" />
</div>
</div>
</div>
</div>
<div class="one-third" style="float: right; margin-top: 0;">
<div id="summary">
<h3>Yard Lad Service Estimate</h3>
<p>This is an initial Yard Lad estimate. The end total may be higher or lower based upon the contractor you choose,
as well as the contractors on-site assessment. Payment adjustments are easy to make on site or online after the
service has been completed.</p>
<div style="font-weight: bold;">Subtotal: $<span class="subtotal">0.00</span></div>
</div>
</div>
<input type="hidden" class="stateId" name="StateId" value="0" />
<input type="hidden" class="serviceAreaId" name="ServiceAreaId" value="0" />
<input type="hidden" class="serviceId" name="ServiceId" value="0" />
更改Ajax调用后“url”服务器错误略有改变。我提供了以下更新的图片： Server Error Image
答案 0 :(得分：0)
当您的服务器收到HTTP Get请求时，它会在请求标头中的url（ex Service / GetServices / 1）内的查询字符串中出现Id。您的ID实际上在请求正文中而不是在url中。这就是您的服务器代码抱怨的原因。要使其工作，您可以将JavaScript代码更改为
function GetServices() {
$.ajax({
type: "GET",
url: "/Service/GetServices/?serviceId=" + $('#ServiceAreaId').val(),
dataType: "jsonp",
async: true
})
.done(function (services) {
$('#ServiceId').empty(); //commenting this line gets the field to never populate with nulls, leaving the
//"loading services..." there permanently, also brings up the request a contractor button.
$.each(services, function (i, service) { //the i is the index being passed to it... service is the value
$("#ServiceId").append(
$('<option/>')
.attr('value', this.ServiceId)
.text(this.Name)
);
});
GetServiceDescription();
});
}