Question

我正在尝试以编程方式访问此网页中的文本框，但我得到“对象引用未设置为对象实例”。这是我的C＃程序

HttpWebRequest request = (HttpWebRequest)WebRequest.Create(mainURL);

//设置标题＆amp;用户代理

request.ContentType = "charset=iso-8859-7;windows-1253;charset=iso-8859-8;windows-1254;";
WebClient wc = new WebClient();
WebBrowser b = new WebBrowser();
wc.Encoding = Encoding.UTF8;
try
{
   b.Navigate(mainURL);
   while (b.ReadyState != WebBrowserReadyState.Complete)
   {
       Application.DoEvents();
    }
    MessageBox.Show("Loaded");
    HtmlElement userName = b.Document.GetElementById("jm");
    userName.SetAttribute("value", "AA");

此网址的HTML是

    <html>
   <head>
<title>ARES - Economic entities - Entry form</title>
  <meta content="text/html;ISO-8859-2" http-equiv="Content-type">
  <link rel="stylesheet" type="text/css" href="css_form.css" media="all"> 
  <link rel="stylesheet" type="text/css" href="css_general.css" media="all">
  <style type="text/css">
      /* explicit attribute of form elements - xx */
      #jm   {width: 13em;}
      #vyst {width: 10em;}
      #ob   {width: 13em;}
      #ic   {width: 8.6em; _width: 8.8em;}
      #view {width: 10em;}   
  </style>
  <script language="JavaScript" type="text/javascript" src="js_cookie.js"></script>
  <script language="JavaScript" type="text/javascript" src="js_form.js.en"></script>
</head>
<body class="BForm" id="FES"> 
<form name="f_ares_frup" action="/cgi-bin/ares/ares_es.cgi" method="get" target="vystup">
<input name="jazyk" type="hidden" value="en">
<div>
  <table class="TForm">
    <tr>
      <td class="ttl">Business name:</td>
      <td class="inp"><input id="jm" name="obch_jm" maxlength="255" size="20" tabindex="2"></td>
      <td class="ttl">Reg.No.:</td>
      <td class="inp"><input class="FFocus" id="ic" maxlength="8" name="ico" size="8" tabindex="1"></td>
          </tr>
    <tr>
     <td class="ttl">View:</td>
      <td class="inp">
      <select id="view" name="maxpoc" tabindex="13">
            <option selected="selected" value="200">200 rec.</option>
            <option value="500">500 rec.</option>
            <option value="1000">1000 rec.</option>
      </select>
          </td>
    </tr>
    <tr>  
    </tr>
    <tr>
<td colspan="6" class="TButtArea"><input alt="LookUp" class="aresButt" type="submit" value="Search" tabindex="16"></td>
</tr>
  </table>
</div>
</form>              
</body>
</html>

我错过了什么？谢谢 Rashmi

访问网页上的TextBox

0 个答案: