How to Extract Data from HTML Elements Within Frames and IFrames?

Parse HTML elements within frames and iframes

You are having trouble finding the <video></video> tag while trying to extract a video link from the provided website. This is because the website uses frames (iframes), which effectively isolate different parts of the content into separate HTML documents.

To solve this problem, you need to dig into the collection of frames in the main document. Each frame contains its own HTML document, and access to these individual documents is necessary to extract data from all parts of the website.

Solution:

Use the WebBrowser.Document.Window.Frames attribute to access the frame collection. Each HtmlWindow in this collection has its own HtmlDocument object.

Modify your code to iterate over each frame's document, using the Frame.Document.Body.GetElementsByTagName() method to retrieve the element you need. Use HtmlElement.GetAttribute to extract element attributes.

Example:

List<MovieLink> moviesLinks = new List<MovieLink>();

private void Browser_DocumentCompleted(object sender, WebBrowserDocumentCompletedEventArgs e)
{
    var browser = sender as WebBrowser;
    if (browser.ReadyState != WebBrowserReadyState.Complete) return;

    var documentFrames = browser.Document.Window.Frames;
    foreach (HtmlWindow frame in documentFrames)
    {
        try
        {
            var videoElement = frame.Document.Body
                .GetElementsByTagName("VIDEO").OfType<HtmlElement>().FirstOrDefault();

            if (videoElement != null)
            {
                string videoLink = videoElement.GetAttribute("src");
                int hash = videoLink.GetHashCode();
                if (moviesLinks.Any(m => m.Hash == hash))
                {
                    return; // 此 URL 的解析已完成
                }

                string sourceImage = videoElement.GetAttribute("poster");
                moviesLinks.Add(new MovieLink()
                {
                    Hash = hash,
                    VideoLink = videoLink,
                    ImageLink = sourceImage
                });
            }
        }
        catch (UnauthorizedAccessException) { } // 忽略此异常
        catch (InvalidOperationException) { } // 忽略此异常
    }
}

Instructions:

• The DocumentCompleted event may fire multiple times as the browser loads each frame document.
• Some frames may not be accessible, or their elements may throw exceptions when accessing properties. Ignore these exceptions because they are unavoidable.
• Use hashing to avoid duplicate link storage. When a duplicate hash value is found, you can stop parsing the URL.

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