asp.net - 当 ModelState 有错误时，"Value cannot be null or empty. Parameter name: contentPath"在回发时最意外的行上

Question

我已经连续两个小时与这个怪物讨价还价了。

我收到此错误:

Value cannot be null or empty. Parameter name: contentPath

在我看来这一行:

@Html.ValidationMessageFor(model => model.IssueName, 
  "", new { @class = "text-danger" })

下面给出的堆栈跟踪似乎表明调用 Url.Content已经打过，但我没有打过这样的电话。下面是堆栈跟踪，然后是导致错误的行周围的更多代码行:

[ArgumentException: Value cannot be null or empty. Parameter name: contentPath] System.Web.Mvc.UrlHelper.GenerateContentUrl(String contentPath, HttpContextBase httpContext) +125
System.Web.Mvc.UrlHelper.Content(String contentPath) +26
ASP._Page_Views_Journal_EditIssue_cshtml.Execute() in MyProject\Views\Journal\EditIssue.cshtml:45
System.Web.WebPages.WebPageBase.ExecutePageHierarchy() +197
System.Web.Mvc.WebViewPage.ExecutePageHierarchy() +105
System.Web.WebPages.StartPage.RunPage() +17
System.Web.WebPages.StartPage.ExecutePageHierarchy() +64
System.Web.WebPages.WebPageBase.ExecutePageHierarchy(WebPageContext pageContext, TextWriter writer, WebPageRenderingBase startPage) +78
System.Web.Mvc.RazorView.RenderView(ViewContext viewContext, TextWriter writer, Object instance) +256
System.Web.Mvc.BuildManagerCompiledView.Render(ViewContext viewContext, TextWriter writer) +107
System.Web.Mvc.ViewResultBase.ExecuteResult(ControllerContext context) +291 System.Web.Mvc.ControllerActionInvoker.InvokeActionResult(ControllerContext controllerContext, ActionResult actionResult) +13
System.Web.Mvc.ControllerActionInvoker.InvokeActionResultFilterRecursive(IList1 filters, Int32 filterIndex, ResultExecutingContext preContext, ControllerContext controllerContext, ActionResult actionResult) +56
System.Web.Mvc.ControllerActionInvoker.InvokeActionResultFilterRecursive(IList1 filters, Int32 filterIndex, ResultExecutingContext preContext, ControllerContext controllerContext, ActionResult actionResult) +420
System.Web.Mvc.ControllerActionInvoker.InvokeActionResultWithFilters(ControllerContext controllerContext, IList1 filters, ActionResult actionResult) +52
System.Web.Mvc.Async.<>c__DisplayClass2b.<BeginInvokeAction>b__1c() +173 System.Web.Mvc.Async.<>c__DisplayClass21.<BeginInvokeAction>b__1e(IAsyncResult asyncResult) +100
System.Web.Mvc.Async.WrappedAsyncResult1.CallEndDelegate(IAsyncResult asyncResult) +10
System.Web.Mvc.Async.WrappedAsyncResultBase1.End() +49
System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeAction(IAsyncResult asyncResult) +27
System.Web.Mvc.Controller.<BeginExecuteCore>b__1d(IAsyncResult asyncResult, ExecuteCoreState innerState) +13
System.Web.Mvc.Async.WrappedAsyncVoid1.CallEndDelegate(IAsyncResult asyncResult) +29
System.Web.Mvc.Async.WrappedAsyncResultBase1.End() +49
System.Web.Mvc.Controller.EndExecuteCore(IAsyncResult asyncResult) +36 System.Web.Mvc.Controller.<BeginExecute>b__15(IAsyncResult asyncResult, Controller controller) +12
System.Web.Mvc.Async.WrappedAsyncVoid1.CallEndDelegate(IAsyncResult asyncResult) +22
System.Web.Mvc.Async.WrappedAsyncResultBase1.End() +49
System.Web.Mvc.Controller.EndExecute(IAsyncResult asyncResult) +26
System.Web.Mvc.Controller.System.Web.Mvc.Async.IAsyncController.EndExecute(IAsyncResult asyncResult) +10
System.Web.Mvc.MvcHandler.<BeginProcessRequest>b__5(IAsyncResult asyncResult, ProcessRequestState innerState) +21
System.Web.Mvc.Async.WrappedAsyncVoid1.CallEndDelegate(IAsyncResult asyncResult) +29
System.Web.Mvc.Async.WrappedAsyncResultBase`1.End() +49
System.Web.Mvc.MvcHandler.EndProcessRequest(IAsyncResult asyncResult) +28 System.Web.Mvc.MvcHandler.System.Web.IHttpAsyncHandler.EndProcessRequest(IAsyncResult result) +9
System.Web.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +9644097 System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +155

引发异常的行周围的代码行是:

<div class="form-group">
    @Html.LabelFor(model => model.IssueName, htmlAttributes: new { @class = "control-label col-md-2"})
    <div class="col-md-10">
        @Html.EditorFor(model => model.IssueName, new { htmlAttributes = new { @class = "form-control", id = "IssueName" } })
        @Html.ValidationMessageFor(model => model.IssueName, "", new { @class = "text-danger" })
    </div>
</div>

重要信息

奇怪的是，只有当我从 post-back 返回时才会引发异常，而不会在我第一次加载 View 时引发异常，甚至在 ModelState 时也不会引发异常。没有错误。它仅在 ModelState 时引发回发后有错误。

这是一些服务器端代码，但我没有看到它可能做错的任何原因:

[HttpPost]
public async Task<ActionResult> EditIssue(EditIssueViewModel viewModel)
{
    viewModel.AvailableTags = BusinessManager.GetAllTags();

    if (viewModel.IssuePDFFile == null || viewModel.IssuePDFFile.ContentLength == 0)
    {
        ModelState.AddModelError("", "Please select a file to upload.");
        return View(viewModel);
    }

    var fileInfo = new FileInfo(viewModel.IssuePDFFile.FileName);
    if (!StaticData.AcceptedContentTypes.Contains(viewModel.IssuePDFFile.ContentType, StringComparer.InvariantCultureIgnoreCase) ||
        !fileInfo.Extension.Equals(".pdf", StringComparison.InvariantCultureIgnoreCase))
    {
        ModelState.AddModelError("", "You can only select a PDF file.");
        return View(viewModel);
    }

    if (!ModelState.IsValid)
    {
        var errors = ModelState.Values.SelectMany(v => v.Errors)
            .Select(e => new { e.ErrorMessage, e.Exception });

        var errorList = errors.ToList();

        errorList.ForEach(e => Debug.Print(e.ErrorMessage));
        errorList.ForEach(e => ModelState.AddModelError("", e.ErrorMessage));

        return View(viewModel);
    }

    var operationResult = await BusinessManager.EditIssueAsync(viewModel);

    if (!operationResult.Succeeded)
    {
        ModelState.AddModelError("", operationResult.FailureMessage);
        return View(viewModel);
    }

    viewModel = (EditIssueViewModel)BusinessManager.GetIssueWithRelationships(viewModel.IssueId);
    viewModel.SuccessMessage = operationResult.SuccessMessage;
    return View(viewModel);
}

Answer 1

碉堡了!

如果您曾经，曾经，曾经遇到过此错误，请记住，导致此错误的原因只有一个，并且只有一个。

Somewhere in the network of lines on your view, you have passed a null value to the @Url.Content method. Period.

它报告异常的行可能与异常无关，并且可能距离罪魁祸首一两英里。

搜索，搜索，疯狂地搜索。 :-)

这就是我如何找到解决方案并从我的痛苦中解脱出来的方法。