asp.net - 什么可能导致 XML 解析错误 : no element found?

Question

我最近将一个 ASP 站点从我的开发机器迁移到了实时服务器。除了我的常见问题页面之外的所有页面都可以正常工作，但我的常见问题解答显示:

XML Parsing Error: no element found
Location: http://geniusupdate.com/GSHelp/faq.aspx
Line Number 1, Column 1:

我所做的唯一更改是将我的 SQL 页面上的连接字符串从本地更改为我的托管服务指定的字符串。关于我可以做些什么来找到这个问题的根源的任何提示？

这是我的常见问题页面的来源:

<%@ Page Language="VB" MasterPageFile="~/theMaster.master" AutoEventWireup="false" CodeFile="faq.aspx.vb" Inherits="faq" Title="Untitled Page" %>
<%@ Import Namespace="sqlstuff" %>
<%@ Import Namespace="functions" %>

<asp:Content ContentPlaceHolderID="page_title" ID="theTitle" runat="server">
    FAQ</asp:Content>
<asp:Content ContentPlaceHolderID="column1_title" ID="col1Title" runat="server">
    <%=faqPageTitle(Request.QueryString("cid"))%></asp:Content>
<asp:Content ContentPlaceHolderID="column1" ID="columnContent" runat="server">

     <p>Click on a question to expand it to see the answer!</p>
     <p><%  If cID >= 0 Then
                Dim theFaq As New List(Of faqContent), iterate As Integer = 0
                theFaq = sqlStuff.getFaqs(cID)
                For Each oFaq As faqContent In theFaq
                    Response.Output.WriteLine("<h4 id={0} class={1}>Q: {2}</h4>", _
                                                 addQuotes("gsSwitch{0}-title", iterate), _
                                                 addQuotes("handCursor"), _
                                                 oFaq.Content.Question)
                    Response.Output.WriteLine("<div id={0} class={1}><string>A: </strong>{2}</div>", _
                                                 addQuotes("gsSwitch{0}", iterate), _
                                                 addQuotes("gsSwitch"), _
                                                 oFaq.Content.Answer)

                    iterate += 1
                Next
            Else
                Response.Output.Write("Here you can find a lot of information about eTHOMAS and how to expedite your office tasks.{0}", ControlChars.NewLine)
            End If
    %></p>
    <script type="text/javascript">
        var gsContent = new switchcontent("gsSwitch", "div")
        var eID = '<%= expandID %>'
        gsContent.collapsePrevious(true) // TRUE: only 1; FALSE: any number
        gsContent.setPersist(false)
        if(eID >= 0){
            gsContent.defaultExpanded(eID) // opens the searched FAQ
            document.getElementById('gsSwitch' + eID + '-title').scrollIntoView(true) // scrolls to selected FAQ
        }        
        gsContent.init()
    </script>
</asp:Content>
<asp:Content ContentPlaceHolderID="subcolumn_right_title" ID="rSideColTitle" runat="server"></asp:Content>
<asp:Content ContentPlaceHolderID="subcolumn_right" ID="rSideColContent" runat="server"></asp:Content>
<asp:Content ContentPlaceHolderID="subcolumn_left_title" ID="lSideColTitle" runat="server"></asp:Content>
<asp:Content ContentPlaceHolderID="subcolumn_left" ID="lSideColContent" runat="server"></asp:Content>
<asp:Content ContentPlaceHolderID="sidecolumn_title" ID="sideColtitle" runat="server">
</asp:Content>
<asp:Content ContentPlaceHolderID="sidecolumn" ID="sideCol" runat="server">
    <%  If cID >= 0 Then
            Response.Write(constructFaqSideMenu(CInt(Request.QueryString("cid"))))
        Else
            Response.Write(constructFaqSideMenu())
        End If
    %>
</asp:Content>

我在另一个论坛上找到了这个 link :

Well, it appears it's a bit of both. The message is generated by Firefox, but caused by the framework. For some reason, .NET generates a response type of "application/xml" when it creates an empty page. Firefox parses the file as XML and finding no root element, spits out the error message.

IE 不呈现页面，句号。这就是 XML 的来源。

这是constructFaqSideMenu() 函数:

Public Shared Function constructFaqSideMenu(ByVal oSelID As Integer) As String
    Dim oCatList As New List(Of faqCategory)
    Dim oRet As New StringBuilder
    Dim iterate As Integer = 1, extraTag As String = ""

    oCatList = sqlStuff.getFaqCats

    oRet.AppendFormattedLine("<ul id={0}>", addQuotes("submenu"))
    oRet.AppendFormattedLine("    <li id={0}>FAQ Categories</li>", addQuotes("title"))
    For Each category As faqCategory In oCatList
        If iterate = oSelID Then
            extraTag = String.Format(" id={0}", addQuotes("active"))
        Else
            extraTag = ""
        End If
        oRet.AppendFormattedLine("    <li{0}><a href={1}>{2}</a></li>", extraTag, addQuotes("faq.aspx?cid={0}", iterate), StrConv(category.Title,         VbStrConv.ProperCase))
        iterate += 1
    Next
    oRet.AppendLine("</ul>")

    Return oRet.ToString
End Function

这是 IE 返回的空白页面的来源:

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<HTML><HEAD>
<META http-equiv=Content-Type content="text/html; charset=windows-1252"></HEAD>
<BODY></BODY></HTML>

Answer 1

我遇到了这个问题，至少对我来说发现这是因为在 C# WebAPI 2 中，如果您返回一个空的 Ok() 结果，它将返回 XML 作为内容类型。即使您在 WebAPI 配置中覆盖它以永远不返回 XML。所以我的解决方案是在我拥有的基本 Controller 类中创建这个函数，并在需要返回空 OK() JSON 响应的任何地方使用它。可以根据他们的需要使其更先进，但这就是我所做的。我想你也可以使用 AttributeFilter，但我做了这个解决方案，因为它在 Action 中的代码数量相同。

protected IHttpActionResult OKJSONResult()
{
    HttpResponseMessage response = Request.CreateResponse(HttpStatusCode.OK, "", new MediaTypeHeaderValue("application/json"));
    return ResponseMessage(response);
}