Question

I have this piece of code:

string x = textBox1.Text;
string[] list = x.Split(';');
foreach (string u in list)
{
    string url = "http://*********/index.php?n=" + u;
    webBrowser1.Navigate(url);
    webBrowser1.Document.GetElementsByTagName("META");
}

and I’m trying to get the <META> tags to output to a message box, but when I test it out, I keep getting this error:

Object reference not set to an instance of an object.

Answer 1

Your problem is that you’re accessing the Document object before the document has loaded – WebBrowsers are asynchronous. Just parse the HTML using a library like the HTML Agility Pack.

Here’s how you might get the <meta> tags using the HTML Agility Pack. (Assumes using System.Net; and using HtmlAgilityPack;.)

// Create a WebClient to use to download the string:
using(WebClient wc = new WebClient()) {
    // Create a document object
    HtmlDocument d = new HtmlDocument();

    // Download the content and parse the HTML:        
    d.LoadHtml(wc.DownloadString("http://stackoverflow.com/questions/10368605/getelementsbytagname-in-c-sharp/10368631#10368631"));

    // Loop through all the <meta> tags:
    foreach(HtmlNode metaTag in d.DocumentNode.Descendants("meta")) {
        // It's a <meta> tag! Do something with it.
    }
}