Using htmlagility pack to replace src values

Question

I'm using a CMS system for a website. My content contributors have put some very hefty images in the system and have then gone on to resize them in the cms so they are appropriate for the page or article. When a webuser hits that page, they download the full image, even though the contributor has resized the image. I have found a image resizer plugin, and all I need to do is add the width and height parameters behind the image name in src. Doing a search it looks like I should be using the html agility pack to achieve this but can someone help me finish off my code. Ive figured out how to find the img tags within the content, but I dont know how to append src with the width and height.

Old Tag

<img src="/IMG_3556E__sq2.jpg?n=9418" id="/IMG_3556E__sq2.jpg?n=9418" width="83px" height="83px" />

To this - notice src value has changed

<img src="/IMG_3556E__sq2.jpg?width=83&amp;height=83" id="/IMG_3556E__sq2.jpg?n=9418" width="83px" height="83px" />

This is my code so far. All I need is help within the if statement to say if the img tag contains a width or a height, append those to the src attribute.

ContentManager contentManager = new ContentManager();
ContentData Content = contentManager.GetItem(id);

HtmlDocument doc = new HtmlDocument();
doc.LoadHtml(Content.Html);

foreach (HtmlNode node in doc.DocumentNode.SelectNodes("//img/@src"))
{
    if (//img has a width or height, it means image has been resized) {
        //append that nodes src within the content.html with the ?width=x&height=x
    }
}

Answer 1

Try this:

static void Main(string[] args)
{
    var htmlDoc = new HtmlDocument();
    htmlDoc.Load(@"E:\Libs\HtmlAgilityPack.1.4.0\htmldoc.html");

    foreach(HtmlNode node in htmlDoc.DocumentNode
                                   .SelectNodes("//img[@src and (@width or @height)]"))
    {
        var src = node.Attributes["src"].Value.Split('?');

        var width = node.Attributes["width"].Value.Replace("px", "");

        var height = node.Attributes["height"].Value.Replace("px", "");

        node.SetAttributeValue("src",
                                src[0] +
                                string.Format("?width={0}&height{1}", width, height));
    }
}

Answer 2

If you use an XPath that selects only nodes with src and width or height, you can omit the if:

foreach (HtmlNode node in doc.DocumentNode
    .SelectNodes("//img[@src and (@width or @height)]"))
{
    node.SetAttributeValue("src",  ...);
}

but be careful: SelectNodes returns null, if nothing matches - as far as I remember HtmlAgilityPack.