当我使用 XPath 提取数据时，它在 messagebox.show 中没有给出任何响应答案

【问题标题】：When I use XPath to extract data it dosen't give any response in the messagebox.show当我使用 XPath 提取数据时，它在 messagebox.show 中没有给出任何响应
【发布时间】：2019-04-24 23:41:39
【问题描述】：

任何人都可以帮助我在 Google chrome 工具开发中使用 Copy Xpath 来获取此路径：

/html/body/table/tbody/tr/td/table[2]/tbody/tr/td/table[1]/tbody/tr[1]/td[2]/table[2]/tbody/tr[1]/td/div[2]/div[1]/table/tbody/tr/td/table/tbody/tr[2]/td[1]

我使用这段代码中的路径来获取数据：

HtmlAgilityPack.HtmlDocument doc = new HtmlAgilityPack.HtmlDocument();

        doc.LoadHtml(webBrowser1.Document.GetElementById("tablemasterbleue").InnerHtml);

        int i = 2;
        while (doc.DocumentNode.SelectSingleNode("/html/body/table/tbody/tr/td/table[2]/tbody/tr/td/table[1]/tbody/tr[1]/td[2]/table[2]/tbody/tr[1]/td/div[2]/div[1]/table/tbody/tr/td/table/tbody/tr[" + i + "]/td[1]") != null)
        {
            string Code_de_ligne = "";
            string Numero_de_produit = doc.DocumentNode.SelectSingleNode("/html/body/table/tbody/tr/td/table[2]/tbody/tr/td/table[1]/tbody/tr[1]/td[2]/table[2]/tbody/tr[1]/td/div[2]/div[1]/table/tbody/tr/td/table/tbody/tr[" + i + "]/td[1]").InnerText;
            string Desc_prod = doc.DocumentNode.SelectSingleNode("//tbody/tr[" + i + "]/td[5]/span").InnerText;
            string Prix_coutânt = doc.DocumentNode.SelectSingleNode("//tbody/tr[" + i + "]/td[7]/span[2]").InnerText;
            string Prix_de_vente = "";
            string Qte = doc.DocumentNode.SelectSingleNode("//tbody/tr[" + i + "]/td[6]/input").GetAttributeValue("value", "");

            i++;

            MessageBox.Show(Code_de_ligne + "|" + Numero_de_produit + "|" + Desc_prod + " | " + Prix_coutânt + "|" + Prix_de_vente + "|" + Qte);
        }

但它在MessageBox.Show 中没有给出任何响应。

我正在针对这个 HTML 文档执行 XPath：

<html><head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Provincial Tire</title>
<link rel="shortcut icon" href="http://www.provincialtire.net/provt/images/plugin/favicon.ico">
<link href="/designglobal/inosoft/style.css" rel="stylesheet" type="text/css">



<link href="http://www.provincialtire.net/jquery/css/imgpreview.css" rel="stylesheet" type="text/css">
<link rel="stylesheet" href="http://www.provincialtire.net/jquery/css/thickbox.css" type="text/css" media="screen">
<link href="http://www.provincialtire.net/jquery/css/uploadify.css" rel="stylesheet" type="text/css">
<link href="http://www.provincialtire.net/jquery/css/style.css" rel="stylesheet" type="text/css">


<script type="text/javascript" src="http://www.provincialtire.net/jquery/js/jquery-1.3.2.min.js"></script> 
<script type="text/javascript" src="http://www.provincialtire.net/jquery/js/jquery-ui-1.7.2.custom.min.js"></script>


<script type="text/javascript" src="http://www.provincialtire.net/jquery/js/jquery.tablesorter2.min.js"></script> 





<script type="text/javascript" src="http://www.provincialtire.net/jquery/js/jquery-thickbox.js"></script>






<script type="text/javascript" src="http://www.provincialtire.net/jquery/js/jquery.tooltips.js"></script>




<script type="text/javascript" src="http://www.provincialtire.net/jquery/js/jquery.imgpreview.js"></script>




<script type="text/javascript" src="http://www.provincialtire.net/jquery/js/jquery.uploadify.v2.1.0.js"></script>
<script type="text/javascript" src="http://www.provincialtire.net/jquery/js/swfobject.js"></script>














<script type="text/javascript">




        function envoieRequete(url,id)
        {
            var xhr_object = null;
            var position = id;

               if(window.XMLHttpRequest)  xhr_object = new XMLHttpRequest();
              else
                if (window.ActiveXObject)  xhr_object = new ActiveXObject("Microsoft.XMLHTTP"); 

            // On ouvre la requete vers la page désirée
            xhr_object.open("GET", url, true);


            document.getElementById(position).innerHTML = "<center><img src=\"http://www.provincialtire.net/provt/images/load.gif\" ><\/center>";


            xhr_object.onreadystatechange = function(){
            if ( xhr_object.readyState == 4 )
            {

                // j'affiche dans la DIV spécifiées le contenu retourné par le fichier
                document.getElementById(position).innerHTML = xhr_object.responseText;



            }
            }
            // dans le cas du get


            xhr_object.send(null);

        }
 </script>















<script type="text/javascript">


function pausecomp(millis) 
{
var date = new Date();
var curDate = null;

do { curDate = new Date(); } 
while(curDate-date < millis);
} 





        function envoieRequeteWait(url,id)
        {

            pausecomp(5);

            var xhr_object = null;
            var position = id;

               if(window.XMLHttpRequest)  xhr_object = new XMLHttpRequest();
              else
                if (window.ActiveXObject)  xhr_object = new ActiveXObject("Microsoft.XMLHTTP"); 

            // On ouvre la requete vers la page désirée
            xhr_object.open("GET", url, true);


            document.getElementById(position).innerHTML = "<center><img src=\"http://www.provincialtire.net/provt/images/load.gif\" ><\/center>";


            xhr_object.onreadystatechange = function(){
            if ( xhr_object.readyState == 4 )
            {

                // j'affiche dans la DIV spécifiées le contenu retourné par le fichier
                document.getElementById(position).innerHTML = xhr_object.responseText;



            }
            }
            // dans le cas du get


            xhr_object.send(null);

        }
 </script>














<script type="text/javascript">

function envoieRequeteSearch(url,id)
        {
 var sid = "2nmia7njlrrc8a9mn5199do5d5";  
            var xhr_object = null;
            var position = id;

               if(window.XMLHttpRequest)  xhr_object = new XMLHttpRequest();
              else
                if (window.ActiveXObject)  xhr_object = new ActiveXObject("Microsoft.XMLHTTP"); 

            // On ouvre la requete vers la page désirée
            xhr_object.open("GET", url, true);
            xhr_object.setRequestHeader('Set-Cookie', 'PHPSESSID=' + sid); 

            document.getElementById(position).innerHTML = "<br><br><table align=\"center\" border=\"0\" height=\"250\" width=\"350\" style=\"background-image:url(/designglobal/inosoft/loading_box.png)\"><tr><td align=\"center\"><img src=\"http://www.provincialtire.net/provt/images/plugins/logoajaxc.gif\" ><br><br><b>Please be patient....<\/b><br><\/td><\/tr><\/table><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br>";


            xhr_object.onreadystatechange = function(){
            if ( xhr_object.readyState == 4 )
            {


                // j'affiche dans la DIV spécifiées le contenu retourné par le fichier
                document.getElementById(position).innerHTML = xhr_object.responseText;















              $(document).ready(function() { 
                  $("table").tablesorter({ 
                      // pass the headers argument and assing a object 
                      headers: { 
                          // assign the secound column (we start counting zero) 
                          9: { 
                              // disable it by setting the property sorter to false 
                              sorter: false 
                          },                      
                            // assign the third column (we start counting zero) 
                          8: { 
                              // disable it by setting the property sorter to false 
                              sorter: false 
                          } 
                      }

                  }); 
              });




                $(document).ready(function() { 
                /*$('a#first').imgPreview();*/
                $('a#first').imgPreview({
                    imgCSS: { width: 250 }
                }); });





            }
            }
            // dans le cas du get



            xhr_object.send(null);

        }
 </script>
















<script type="text/javascript">

function Requete(url,id)
        {
 var sid = "2nmia7njlrrc8a9mn5199do5d5";  
            var xhr_object = null;
            var position = id;

               if(window.XMLHttpRequest)  xhr_object = new XMLHttpRequest();
              else
                if (window.ActiveXObject)  xhr_object = new ActiveXObject("Microsoft.XMLHTTP"); 

            // On ouvre la requete vers la page désirée
            xhr_object.open("GET", url, true);
            xhr_object.setRequestHeader('Set-Cookie', 'PHPSESSID=' + sid); 

            document.getElementById(position).innerHTML = "<img src=\"http://www.provincialtire.net/provt/images/pbar.gif\" >";


            xhr_object.onreadystatechange = function(){
            if ( xhr_object.readyState == 4 )
            {


                // j'affiche dans la DIV spécifiées le contenu retourné par le fichier
                document.getElementById(position).innerHTML = xhr_object.responseText;

            }
            }
            // dans le cas du get



            xhr_object.send(null);

        }
 </script>










<script type="text/javascript"> 

function stopRKey(evt) { 
  var evt = (evt) ? evt : ((event) ? event : null); 
  var node = (evt.target) ? evt.target : ((evt.srcElement) ? evt.srcElement : null); 
  if ((evt.keyCode == 13) && (node.type=="text"))  {return false;} 
} 

document.onkeypress = stopRKey; 

</script>





<script type="text/javascript">


function toggle(anId)
{
    node = document.getElementById(anId);
    if (node.style.visibility=="hidden")
    {
        // caché vers montrer
        node.style.visibility = "visible";
        node.style.height = "auto";         
    }
    else
    {
        // visible vers cacher
        node.style.visibility = "hidden";
        node.style.height = "0";            
    }
}

</script>





<script type="text/javascript">
        function blocknumber(event) {
        // Compatibilité IE / Firefox
        if(!event&&window.event) {
        event=window.event;
        }
        // IE
        if(event.keyCode < 48 || event.keyCode > 57) {
        event.returnValue = false;
        event.cancelBubble = true;
        }
        // DOM
        if(event.which < 48 || event.which > 57) {
        event.preventDefault();
        event.stopPropagation();
        }
        }   




function blockletter(evt) {
    var e = evt || window.event;
    var key = e.keyCode || e.which;

    if (!e.shiftKey && !e.altKey && !e.ctrlKey &&
    // numbers   
    key >= 48 && key <= 57 ||
    // Numeric keypad
    key >= 96 && key <= 105 ||
    // Backspace and Tab and Enter
    key == 8 || key == 9 || key == 13 ||
    // Home and End
    key == 35 || key == 36 ||
    // left and right arrows
    key == 37 || key == 39 ||
    // Del and Ins
    key == 46 || key == 45 ||
    // point .
    key == 110) {
        // input is VALID
    }
    else {
        // input is INVALID
        e.returnValue = false;
        if (e.preventDefault) e.preventDefault();
    }
}

</script>    



<script type="text/JavaScript">
<!--
function timedRefresh(timeoutPeriod) {
    theUrl = 'http://www.provincialtire.net/search.html';

    setTimeout("location.replace(theUrl);",timeoutPeriod);
}
//  JavaScript:timedRefresh(1000000); -->
</script>




<script>
function SendInfo(e){

    if(e){
        e = e 
        } else {
        e = window.event
    } 

    if(e.which){ 
    var keycode = e.which
    } else {
    var keycode = e.keyCode 
    }

    if(keycode == 13) { 
         envoieRequeteSearch('modules/searchajax.php?size='+form1.size.value+'&manu='+form1.manu.value+'&desc='+form1.desc.value+'&type='+form1.type.value+'&nostock='+form1.nostock.checked+'&prodno='+form1.prodno.value+'&tri='+form1.tri.value+'&cache='+form1.cache.checked,'conteneur');      

    }

}
</script>

















<script type="text/javascript">if (window != top) top.location.href = location.href;</script>
<noscript>
You do Activate JavaScript on your Brwoser / Vous devez activer le JavaScript de votre navigateur
</noscript>


</head>

<body onload=" ">





<table width="960" border="0" align="center">
  <tbody><tr>
    <td>


    <table width="100%" border="0" align="center" cellpadding="0" cellspacing="0">
                <tbody><tr>
          <td valign="top">


          <table width="100%" border="0" cellspacing="0" cellpadding="0" style="background-image:url(http://www.provincialtire.net/provt/images/plugins/toplogo.jpg)">
            <tbody><tr>
              <td>&nbsp;</td>
              <td>&nbsp;</td>
              <td>&nbsp;</td>
              <td width="392" height="110">

          <div style="position:relative;">

            <div style="position:absolute; bottom:35px; right:5px;">
              <a href="exit-en.html"> <img src="http://www.provincialtire.net/images/error.png" title="Exit"> </a>
            </div>

         </div>                    


                </td>
              </tr>
            </tbody></table>

           </td>
        </tr>
      </tbody></table>


      <table width="960" border="0" align="center" cellpadding="0" cellspacing="0">
        <tbody><tr>
          <td valign="top" background="/designglobal/inosoft/background.jpg" style="background-repeat:no-repeat;" bgcolor="#ffffff">
















        <div style="position:relative; top:-5px;">

          <table style="background-image:url(/designglobal/inosoft/top_menu_button.jpg)" border="0" cellspacing="0" cellpadding="0" height="45" id="cellule_menu_principal">
            <tbody><tr>


              <td width="50" align="center" class="menu_principal">&nbsp;   </td>

              <td width="96" align="center" class="menu_principal">                 <a style="" href="/">Informations</a>  </td>

              <td width="96" align="center" class="menu_principal">             <a style="" href="promotions-en.html">Promotions</a> </td>

              <td width="96" align="center" class="menu_principal">             <a style="color:#FF0000" href="search-en.html">Search <br> Products</a> </td>

              <td width="96" align="center" class="menu_principal">                 <a style="" href="acount-en.html">Your Account</a> </td>

              <td width="96" align="center" class="menu_principal">             <a style="" href="storage-en.html">Your<br>Storage</a> </td>

              <td width="96" align="center" class="menu_principal">
              &nbsp;              
              </td>

              <td width="96" align="center" class="menu_principal">                  <a style="" href="tracking-en.html">Track Shipments</a> </td>

              <td width="96" align="center" class="menu_principal">             <a style="" href="tools-en.html">Tools</a> </td>

              <td width="80" align="center" class="menu_principal"><a href="modules/rma.php?l=en&amp;noclient=73742&amp;keepThis=true&amp;TB_iframe=true&amp;height=350&amp;width=475" title="RMA" class="thickbox">
                              RMA              </a></td>

              <td width="96" align="center" class="menu_principal">                  <a style="" href="contact-en.html">Contact Us</a> </td>
            </tr>


          </tbody></table>

        </div> 


















            <table width="100%" height="1000" border="0" cellpadding="0" cellspacing="0">
              <tbody><tr>
              <td width="15">&nbsp;</td>
              <td class="texte" valign="top"><br>












          <table width="100%" border="0" cellpadding="0">
            <tbody><tr>
              <td width="120">



              <table height="36" border="0" cellpadding="0" cellspacing="0" background="http://www.provincialtire.net/provt/images/topbutton/img_fond_titre.jpg">
                <tbody><tr>
                  <td valign="middle" class="titre"><img src="http://www.provincialtire.net/provt/images/topbutton/img_cote_gauche_titre.jpg" width="12" height="39"></td>
                  <td valign="top" class="titre"><table border="0" cellspacing="0" cellpadding="0">
                      <tbody><tr>
                        <td height="5"></td>
                      </tr>
                      <tr>
                        <td>

                        Order                        
                        </td>
                      </tr>
                  </tbody></table></td>
                  <td width="16" align="right" valign="middle"><img src="http://www.provincialtire.net/provt/images/topbutton/img_cote_droit_titre.jpg" width="12" height="39"></td>
              </tr>
            </tbody></table>


            </td>


              <td>&nbsp;











              </td>





            </tr>
          </tbody></table>






<br>




<table width="100%" cellpadding="4" cellspacing="4"><tbody><tr><td>
















<div class="dialog"> <div class="boxContent"> <div class="t"></div> 






<a style="color:#FFFFFF" href="/?ordernow=y&amp;rem=all">Delete All Products</a>



&nbsp;



</div> <div class="b"> <div> </div> </div> </div> 
















<div class="dialog"> <div class="boxContent"> <div class="t"></div> 






<table border="1" cellpadding="0" cellspacing="0" bordercolor="#FFD700" width="100%"><tbody><tr valign="top"><td valign="top">  

 &nbsp;&nbsp;<br><table class="tablemasterbleue" style="font-size:11px;" width="100%" border="0" cellpadding="0" cellspacing="0">
    <tbody><tr class="headerlist">
        <td width="100" align="center">Prod #</td>
        <td width="100" align="center">Manufacturer</td>
        <td width="75" align="center">Qty</td>
        <td width="35"></td>
        <td width="35"></td>
        <td width="">Description</td>
        <td width="35"></td>
        <td width="100" align="center">Price</td>
    </tr>


        <tr style="padding: 0px 10px 0px 10px; color:#000000; height:40px;" bgcolor="#EDEDED">
            <td align="left" width="125">&nbsp; <a href="/?ordernow=y&amp;rem=order&amp;prod=1"><img src="http://www.provincialtire.net/images/redcross.png"></a> &nbsp; 00959</td>
            <td align="center"><img title="" width="75" height="27" src="http://www.provincialtire.net/provt/images/plugins/logo/UNIR.gif"></td>
            <td align="center"> 4 </td>
            <td align="left">-</td><td> <img width="30" src="http://www.provincialtire.net/provt/images/plugins/type/W.png"> </td>
                <td align="left">&nbsp;&nbsp;205/60R16 Tiger Paw Ice &amp; Snow 3 </td>
            <td align="right"><div id="each1"><b></b></div></td><td style="background-image:url(/images/special.gif); background-repeat:no-repeat; background-position:top" align="center"><b>95.00</b></td>
    </tr><tr class="headerlist"><td colspan="8">

        <table width="100%" style="font-size:12px; font-weight:bold;" border="0">
            <tbody><tr style="color:#FFFFFF">
                <td colspan="3">&nbsp;</td>
                <td width="50">HST</td>
                <td width="25">

                <div id="tps">

                49.4                
                </div>



                </td>
            </tr>
            <tr style="color:#FFFFFF">
                <td colspan="3">&nbsp;</td>
                <td width="50"></td>
                <td width="25">


                <div id="tvq">





                </div>


                </td>
            </tr>
            <tr style="color:#FFFFFF">
                <td colspan="3">&nbsp;</td>
                <td width="50">TOTAL</td>
                <td width="25">
                    <div id="total">
                        429.4                
                    </div>
                </td>
            </tr>
        </tbody></table>

    </td></tr>

</tbody></table>






</td></tr></tbody></table>


<br><br>






</div> <div class="b"> <div> </div> </div> </div> 

</td></tr>

<tr><td>


</td></tr>

<tr><td>
<form id="form1" name="form1" method="post" action="/sendorder-en.html">

<div class="dialog"> <div class="boxContent"> <div class="t"></div>  


 <table style="color:#FFFFFF" width="100%" border="0" cellpadding="3" cellspacing="5">


          <tbody><tr>
            <td colspan="2" align="right">




              <br><b>This order does not apply to a national account<b><br><input type="hidden" value="n" name="clinat" id="clinat">       






               </b></b></td>
            </tr>


            <tr>
              <td>&nbsp;</td>
              <td>&nbsp;</td>
            </tr>
            <tr>
              <td width="50%"><b>Delivery Instruction: </b></td>
              <td width="50%"><input type="hidden" value="y" name="basketsend" id="basketsend"><input type="hidden" value="y" name="type" id="type"></td>
              </tr>
            <tr>
              <td rowspan="3" align="left" valign="top"><label>
                <input name="instruction" type="text" id="instruction" value="" maxlength="68" size="50">
              </label></td>
            <td align="right">



    <table cellpadding="3" cellspacing="3" border="0">
      <tbody><tr>
         <td align="right">
            <input type="radio" name="radio" id="radio" value="radio1" checked="checked">Next delivery 
            <input type="radio" name="radio" id="radio" value="radio2">Morning 
            <input type="radio" name="radio" id="radio" value="radio3">Afternoon    
        </td>
        </tr>

        <tr>
         <td align="right">   
             <input type="radio" name="radio" id="radio" value="radio4">Tomorrow Morning                
             <input type="radio" name="radio" id="radio" value="radio5">Tomorrow Afternoon   
          </td>
          </tr><tr>
          <td align="right">   
             <input type="radio" name="radio" id="radio" value="radio8">Standard Delivery                   
             <input type="radio" name="radio" id="radio" value="radio9">Urgent delivery  
          </td>
          </tr><tr> 
          <td align="right">   
             <input type="radio" name="radio" id="radio" value="radio6">Pick Up                 
              <input type="radio" name="radio" id="radio" value="radio7">See Special Instruction   
          </td>
      </tr>
    </tbody></table>            



    </td>
          </tr>
            <tr>
              <td align="right">&nbsp;</td>
          </tr>
            <tr>
              <td align="right">Purchase Order : 
                <label>
                  <input type="text" name="boncom" id="boncom" maxlength="10">
              </label></td>
              </tr>
            <tr>
              <td align="right">&nbsp;</td>
              <td align="right">&nbsp;</td>
          </tr>
            <tr>
              <td align="right">&nbsp;</td>
              <td align="right"><input class="normal" width="300px" type="submit" name="buttonsend" id="buttonsend" value="Send" onclick="javascript:this.disabled=true;form1.submit();"></td>
              </tr>
        </tbody></table>
</div> <div class="b"> <div> </div> </div> </div>  </form>
</td></tr></tbody></table>
<br>

<script>
$(document).ready(function() { 
/*$('a#first').imgPreview();*/
$('a#first').imgPreview({
    imgCSS: { width: 250 }
}); });

</script>                <br></td>
              <td width="15">&nbsp;</td>
            </tr>
            <tr>
              <td>&nbsp;</td>
              <td align="center">&nbsp;</td>
              <td>&nbsp;</td>
            </tr>
          </tbody></table>
            <table width="960" cellspacing="0" cellpadding="0" class="tablemasterbleueborder" border="3">

              <tbody><tr>
                <td height="36" align="center" valign="middle" bgcolor="#ffffff">

                <table width="100%">
                  <tbody><tr>
                    <td align="center">
                    <a href="http://www.inosoft.ca/english/index.htm"> <img src="images/inosoft-en.jpg" width="125" height="35" alt="InoSoft"> </a>
                    </td>
                  </tr>
                </tbody></table>
                </td>
              </tr>
          </tbody></table></td>
        </tr>
      </tbody></table>
      <br>
      <center>
      <a href="exit-en.html" style="color:#000">Exit</a>
      </center>
    <br></td>
  </tr>
</tbody></table>
<div id="imgPreviewContainer" style="display: none;"><img style="width: 250px;"></div></body></html>

这里也是检查元素的截图：https://i.imgur.com/o59X5wA.png

所以我要使用 xpath 还是需要其他解决方案？

提前谢谢你。

【问题讨论】：

您正在抓取的页面是使用 Javascript 还是 HTML 可以解析？请将您的 XPath 表达式和 HTML 缩减为可发布的内容并发布。没有看到 HTML（和minimal reproducible example），我们无法重现您的情况，然后我们无法真正帮助您。
页面使用 HTML
provincialtire.net/images/redcross.png"></a> 00959
请编辑您的问题并在此处添加其他数据。
我想添加屏幕截图，但他们不允许。

标签： c# html xpath google-chrome-devtools html-agility-pack

【解决方案1】：

实际问题是像//tbody/tr[" + i + "]/td[5]/span 这样的XPath 查询返回null，因为没有对应的span HTML 元素，所以.InnerText 与NullReferenceException 崩溃. td 元素的索引（如td[5]）似乎也是错误的。正确的 XPath 是 //tbody/tr[" + i + "]/td[6]。但是你可以重写你的代码，让它变得更好。

因为要遍历多个产品节点，所以最好使用返回所有匹配节点（产品）的集合的doc.DocumentNode.SelectNodes() 而不是doc.DocumentNode.SelectSingleNode()。每个选定的产品节点看起来都类似于：

<tr style="padding: 0px 10px 0px 10px; color:#000000; height:40px;" bgcolor="#EDEDED">
    <td align="left" width="125">&nbsp; <a href="/?ordernow=y&amp;rem=order&amp;prod=1"><img src="http://www.provincialtire.net/images/redcross.png"></a> &nbsp; 00959</td>
    <td align="center"><img title="" width="75" height="27" src="http://www.provincialtire.net/provt/images/plugins/logo/UNIR.gif"></td>
    <td align="center"> 4 </td>
    <td align="left">-</td><td> <img width="30" src="http://www.provincialtire.net/provt/images/plugins/type/W.png"> </td>
    <td align="left">&nbsp;&nbsp;205/60R16 Tiger Paw Ice &amp; Snow 3 </td>
    <td align="right"><div id="each1"><b></b></div></td><td style="background-image:url(/images/special.gif); background-repeat:no-repeat; background-position:top" align="center"><b>95.00</b></td>
</tr>

选择此节点后，您无需再次执行整个复杂的XPath 查询（如/html/body/table/tbody/tr/td/table[2]/tbody/tr/td/table[1]/tbody/tr[1]/td[2]/table[2]/tbody/tr[1]/td/div[2]/div[1]/table/tbody/tr/td/table/tbody/tr[" + i + "]/td[1]）来收集所需的信息。仅对上面选择的 HTML 节点执行 XPath 查询，例如node.SelectSingleNode("td[1]")，不仅更短更易读，而且效率更高。整个代码可能如下所示：

HtmlAgilityPack.HtmlDocument doc = new HtmlAgilityPack.HtmlDocument();
doc.LoadHtml(webBrowser1.Document.GetElementById("tablemasterbleue").InnerHtml);

foreach(var node in doc.DocumentNode
    .SelectNodes("/html/body/table/tbody/tr/td/table[2]/tbody/tr/td/table[1]/tbody/tr[1]/td[2]/table[2]/tbody/tr[1]/td/div[2]/div[1]/table/tbody/tr/td/table/tbody/tr")
    .Skip(1)/*Skip first row containing headers*/)
{
    string Code_de_ligne = "";
    string Numero_de_produit = node.SelectSingleNode("td[1]").InnerText;
    string Desc_prod = node.SelectSingleNode("td[6]").InnerText;
    string Prix_coutânt = node.SelectSingleNode("td[8]").InnerText;
    string Prix_de_vente = "";
    string Qte = node.SelectSingleNode("td[3]").InnerText;

    MessageBox.Show(Code_de_ligne + "|" + Numero_de_produit + "|" + Desc_prod + " | " + Prix_coutânt + "|" + Prix_de_vente + "|" + Qte);
}

由于获取的字符串可能包含过多的 HTML 实体和空格，如“&nbsp; &nbsp; 00959”，您可能需要删除它们：

// Convert string like "&nbsp;  &nbsp; 00959" to just "00959"
Numero_de_produit = HtmlEntity.DeEntitize(Numero_de_produit).Trim();

【讨论】：

您的代码非常实用，我会使用它，非常感谢您的帮助。 :)
您好，我只想问您，当我在 foreach 行中执行我的代码时，它给了我以下消息错误：System.ArgumentNullException: 'La valeur ne peut pas être null。 Nom du paramètre : 来源'
您好，我只是想问您，当我在 foreach 行中执行我的代码时，它给了我以下消息错误：System.ArgumentNullException：'值不能为空。参数名称：source'
这意味着没有与请求的 XPath /html/body/table/tbody/tr/td/table[2]/tbody/tr/td/table[1]/tbody/tr[1]/td[2]/table[2]/tbody/tr[1]/td/div[2]/div[1]/table/tbody/tr/td/table/tbody/tr 匹配的 HTML 元素。在您提供的 HTML 文档中，有 3 个匹配节点，但如果您尝试使用另一个 HTML 文档，则可能没有这样的元素，在这种情况下 SelectNodes() 返回 null。如果不能保证至少存在 1 个匹配的 HTML 元素，则需要添加 null-check 来处理这种情况。

【解决方案2】：

tablemasterbleue 是 class 不是 id 并且因为没有方法 GetElementsByClassName extract 使用 WebBrowser1.DocumentText 获取页面源然后循环行或 tr。

下面的 xpath 将选择表类 tablemasterbleue 中的行，但如果在顶部和底部存在类 headerlist，则跳过。

doc.LoadHtml(WebBrowser1.DocumentText);

foreach (var node in doc.DocumentNode
    .SelectNodes("//table[@class='tablemasterbleue']/tbody/tr[not(contains(@class, 'headerlist'))]"))
{
    string Code_de_ligne = "";
    string Numero_de_produit = node.SelectSingleNode("td[1]").InnerText;
    string Desc_prod = node.SelectSingleNode("td[6]").InnerText;
    string Prix_coutânt = node.SelectSingleNode("td[8]").InnerText;
    string Prix_de_vente = "";
    string Qte = node.SelectSingleNode("td[3]").InnerText;

    MessageBox.Show(Code_de_ligne + "|" + Numero_de_produit + "|" + Desc_prod + " | " + Prix_coutânt + "|" + Prix_de_vente + "|" + Qte);
}

【讨论】：

不幸的是它对我不起作用，它仍然是同样的错误 System.ArgumentNullException: 'The value can not be null.参数名称：source'
你现在那个null是什么变量？
我认为是源参数。