我尝试了一段视频中的代码，得到了一个错误：
这是我点击下拉菜单显示国家的州时出现的错误
这是我的控制器代码：
public ActionResult Submit()
{
List<Country> allCountry = new List<Country>();
List<State> allState = new List<State>();
using (DropDownTestEntities1 dc = new DropDownTestEntities1())
{
allCountry = dc.Countries.OrderBy(a => a.CountryName).ToList();
}
ViewBag.CountryID = new SelectList(allCountry, "CountryID", "CountryName");
ViewBag.StateID = new SelectList(allState, "StateID", "StateName");
return View();
}
[HttpPost]
[ValidateAntiForgeryToken] // this is for prevent CSRF Attack
public ActionResult Submit(Feedback fb)
{
List<Country> allCountry = new List<Country>();
List<State> allState = new List<State>();
using (DropDownTestEntities1 dc = new DropDownTestEntities1())
{
allCountry = dc.Countries.OrderBy(a => a.CountryName).ToList();
if (fb != null && fb.CountryID > 0)
{
allState = dc.States.Where(a => a.CountryID.Equals(fb.CountryID)).OrderBy(a => a.StateName).ToList();
}
}
ViewBag.CountryID = new SelectList(allCountry, "CountryID", "CountryName", fb.CountryID);
ViewBag.StateID = new SelectList(allState, "StateID", "StateName", fb.StateID);
if (ModelState.IsValid)
{
using (DropDownTestEntities1 dc = new DropDownTestEntities1())
{
dc.Feedbacks.Add(fb);
dc.SaveChanges();
ModelState.Clear();
fb = null;
ViewBag.Message = "Successfully submitted";
}
}
else
{
ViewBag.Message = "Failed! Please try again";
}
return View(fb);
}
[HttpGet]
public JsonResult GetStates(string countryID = "")
{
List<State> allState = new List<State>();
int ID = 0;
if (int.TryParse(countryID, out ID))
{
using (DropDownTestEntities1 dc = new DropDownTestEntities1())
{
allState = dc.States.Where(a => a.CountryID.Equals(ID)).OrderBy(a => a.StateName).ToList();
//allState = dc.States.Where(a => a.CountryID.Equals(ID)).OrderBy(a => a.StateName).ToList();
}
}
if (Request.IsAjaxRequest())
{
return new JsonResult
{
Data = allState,
JsonRequestBehavior = JsonRequestBehavior.AllowGet
};
}
else
{
return new JsonResult
{
Data = "Not valid request",
JsonRequestBehavior = JsonRequestBehavior.AllowGet
};
}
}
}
}
这是我的型号代码：
public partial class Feedback
{
public int FeedbackID { get; set; }
[Display(Name = "Full Name")]
[Required(ErrorMessage = "Please provide your fullname", AllowEmptyStrings = false)]
public string FullName { get; set; }
[Display(Name = "Mobile No")]
public string MobileNo { get; set; }
[Display(Name = "Country")]
[Required(ErrorMessage = "Please select country", AllowEmptyStrings = false)]
public int CountryID { get; set; }
[Display(Name = "State")]
[Required(ErrorMessage = "Please select state", AllowEmptyStrings = false)]
public int StateID { get; set; }
}
这是我对ajax代码的看法：
@using (Html.BeginForm("Submit", "Feedback", FormMethod.Post))
{
@Html.ValidationSummary(true)
@Html.AntiForgeryToken()
<fieldset>
<legend>Feedback</legend>
@if (ViewBag.Message != null)
{
<div style="border:solid 1px black">
@ViewBag.Message
</div>
}
<div class="editor-label">
@Html.LabelFor(model => model.FullName)
</div>
<div class="editor-field">
@Html.EditorFor(model => model.FullName)
@Html.ValidationMessageFor(model => model.FullName)
</div>
<div class="editor-label">
@Html.LabelFor(model => model.MobileNo)
</div>
<div class="editor-field">
@Html.EditorFor(model => model.MobileNo)
@Html.ValidationMessageFor(model => model.MobileNo)
</div>
<div class="editor-label">
@Html.LabelFor(model => model.CountryID)
</div>
<div class="editor-field">
@Html.DropDownListFor(model => model.CountryID, @ViewBag.CountryID as SelectList, "Select Country")
@Html.ValidationMessageFor(model => model.CountryID)
</div>
<div class="editor-label">
@Html.LabelFor(model => model.StateID)
</div>
<div class="editor-field">
@Html.DropDownListFor(model => model.StateID, @ViewBag.StateID as SelectList, "Select State")
@Html.ValidationMessageFor(model => model.StateID)
</div>
<p>
<input type="submit" value="Create" />
</p>
</fieldset>
}
<div>
@Html.ActionLink("Back to List", "Index")
</div>
@section Scripts {
@Scripts.Render("~/bundles/jqueryval")
<script language="javascript">
$(document).ready(function () {
$("#CountryID").change(function () {
// this will call when Country Dropdown select change
var countryID = parseInt($("#CountryID").val());
if (!isNaN(countryID)) {
var ddState = $("#StateID");
ddState.empty(); // this line is for clear all items from State dropdown
ddState.append($("<option></option").val("").html("Select State"));
// Here I will call Controller Action via Jquery to load State for selected Country
$.ajax({
url: "@Url.Action("GetStates","Feedback")",
type: "GET",
data: { countryID: countryID },
dataType: "json",
success: function (data) {
$.each(data, function (i, val) {
ddState.append(
$("<option></option>").val(val.StateID).html(val.StateName)
);
});
},
error: function () {
alert("Error!");
}
});
}
});
});
</script>
}
我只想让我的国家选择他们用两者之间的链接来填充我的州。例如，如果我选择南非，它必须只显示豪登省、开普敦等。
请你帮我纠正错误或提供指导，谢谢。
问题1：尝试使用==而不是.Equals()，因为如果CountryID为null，则会引发错误。
问题2：更改
if (Request.IsAjaxRequest())
{
return new JsonResult
{
Data = allState,
JsonRequestBehavior = JsonRequestBehavior.AllowGet
};
}
至
return Json(allState, JsonRequestBehavior.AllowGet);
可能的问题3？试试这个作为你的成功函数：
success: function (data) {
$(data).each(function () {
ddState.append(
$("<option></option>").val(this.StateID).html(this.StateName)
);
});
},