嗯，我查过了。我们使用的 XPath 完全不正确。当您尝试找出错误所在时，真正的乐趣就开始了。
只需检查您正在使用的页面的源代码，除了许多妨碍 XPath 的错误，它甚至包含多个 HTML 标记...
Chrome 开发工具和您使用的工具在浏览器纠正的 dom 树上工作（全部打包到单个 html 节点中，添加了一些 tbody 等）。
由于html结构被简单破坏了，所以变成了HtmlAgilityPack解析。
在这种情况下，您可以使用 RegExp 或只搜索源中的已知元素（这要快得多，但不太灵活）。
例如：
...
using System.Net; //required for Webclient
...
class Program
{
//entry point of console app
static void Main(string[] args)
{
// url to download
// "var" means I am too lazy to write "string" and let compiler decide typing
var url = @"http://www.dsebd.org/displayCompany.php?name=NBL";
// creating object in using makes Garbage Collector delete it when using block ends, as opposed to standard cleaning after whole function ends
using (WebClient client = new WebClient()) // WebClient class inherits IDisposable
{
// simply download result to string, in this case it will be html code
string htmlCode = client.DownloadString(url);
// cut html in half op position of "Last Trade:"
// searching from beginning of string is easier/faster than searching in middle
htmlCode = htmlCode.Substring(
htmlCode.IndexOf("Last Trade:")
);
// select from .. to .. and then remove leading and trailing whitespace characters
htmlCode = htmlCode.Substring("2\">", "</font></td>").Trim();
Console.WriteLine(htmlCode);
}
Console.ReadLine();
}
}
// http://stackoverflow.com/a/17253735/3147740 <- copied from here
// this is Extension Class which adds overloaded Substring() I used in this code, it does what its comments says
public static class StringExtensions
{
/// <summary>
/// takes a substring between two anchor strings (or the end of the string if that anchor is null)
/// </summary>
/// <param name="this">a string</param>
/// <param name="from">an optional string to search after</param>
/// <param name="until">an optional string to search before</param>
/// <param name="comparison">an optional comparison for the search</param>
/// <returns>a substring based on the search</returns>
public static string Substring(this string @this, string from = null, string until = null, StringComparison comparison = StringComparison.InvariantCulture)
{
var fromLength = (from ?? string.Empty).Length;
var startIndex = !string.IsNullOrEmpty(from)
? @this.IndexOf(from, comparison) + fromLength
: 0;
if (startIndex < fromLength) { throw new ArgumentException("from: Failed to find an instance of the first anchor"); }
var endIndex = !string.IsNullOrEmpty(until)
? @this.IndexOf(until, startIndex, comparison)
: @this.Length;
if (endIndex < 0) { throw new ArgumentException("until: Failed to find an instance of the last anchor"); }
var subString = @this.Substring(startIndex, endIndex - startIndex);
return subString;
}
}