TLDR:

1. You need to tellHtmlWebto decompress the response (or use a suitable HTTP client)
2. You need to fix the XPath selector

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Apparently, theSelectSingleNode()call returnsnullbecause it cannot find the node.

In this case, it is helpful to inspect the loaded HTML. You can do this by getting the value ofhtmlDoc.DocumentNode.InnerHtml. I've tried doing this and the "HTML" generated is meaningless.

The reason is thatHtmlWebdoes not decompress the response it receives by default. Seethisgithub issue for details. If you used a proper HTTP client (likethis), or if the HtmlAgilityPack developers were more proactive, I don't think you would run into this problem.

If you insist on usingHtmlWeb, your code should look like this:

const string html = @"https://coinmarketcap.com/currencies/bitcoin/"; var web = new HtmlWeb { AutomaticDecompression = DecompressionMethods.GZip }; HtmlDocument doc = web.Load(html); HtmlNode node = doc.DocumentNode.SelectSingleNode("//div[@class='priceValue ']/span");

Please note that the class of the element you are looking for is actuallypriceValue(with a space character at the end), there is anotheron the page with classpriceValuediv. That's another question, though, and you should eventually be able to find a more robust selector. Maybe try this:

HtmlNode node = doc.DocumentNode.SelectSingleNode("//div[contains(@class, 'priceSection')]//div[contains(@class, 'priceValue')]/span");