Best way to combine nodes with Html Agility Pack

Question

I've converted a large document from Word to HTML. It's close, but I have a bunch of "code" nodes that I'd like to merge into one "pre" node.

Here's the input:

<p>Here's a sample MVC Controller action:</p>
<code>        public ActionResult Index()</code>
<code>        {</code>
<code>            return View();</code>
<code>        }</code>
<p>We'll start by making the following changes...</p>

I want to turn it into this, instead:

<p>Here's a sample MVC Controller action:</p>
<pre class="brush: csharp">        public ActionResult Index()
    {
        return View();
    }</pre>
<p>We'll start by making the following changes...</p>

I ended up writing a brute-force loop that iterates nodes looking for consecutive ones, but this seems ugly to me:

HtmlDocument doc = new HtmlDocument();
doc.Load(file);

var nodes = doc.DocumentNode.ChildNodes;
string contents = string.Empty;

foreach (HtmlNode node in nodes)
{

    if (node.Name == "code")
    {
        contents += node.InnerText + Environment.NewLine;
        if (node.NextSibling.Name != "code" && 
            !(node.NextSibling.Name == "#text" && node.NextSibling.NextSibling.Name == "code")
            )
        {
            node.Name = "pre";
            node.Attributes.RemoveAll();
            node.SetAttributeValue("class", "brush: csharp");
            node.InnerHtml = contents;
            contents = string.Empty;
        }
    }
}

nodes = doc.DocumentNode.SelectNodes(@"//code");
foreach (var node in nodes)
{
    node.Remove();
}

Normally I'd remove the nodes in the first loop, but that doesn't work during iteration since you can't change the collection as you iterate over it.

Better ideas?

Answer 1

The first approach: select all the <code> nodes, group them, and create a <pre> node per group:

var idx = 0;
var nodes = doc.DocumentNode
    .SelectNodes("//code")
    .GroupBy(n => new { 
        Parent = n.ParentNode, 
        Index = n.NextSiblingIsCode() ? idx : idx++ 
    });

foreach (var group in nodes)
{
    var pre = HtmlNode.CreateNode("<pre class='brush: csharp'></pre>");
    pre.AppendChild(doc.CreateTextNode(
        string.Join(Environment.NewLine, group.Select(g => g.InnerText))
    ));
    group.Key.Parent.InsertBefore(pre, group.First());

    foreach (var code in group)
        code.Remove();
}

The grouping field here is combined field of a parent node and group index which is increased when new group is found. Also I used NextSiblingIsCode extension method here:

public static bool NextSiblingIsCode(this HtmlNode node)
{
    return (node.NextSibling != null && node.NextSibling.Name == "code") ||
        (node.NextSibling is HtmlTextNode && 
         node.NextSibling.NextSibling != null && 
         node.NextSibling.NextSibling.Name == "code");
}

It used to determine whether the next sibling is a <code> node.

---

The second approach: select only the top <code> node of each group, then iterate through each of these nodes to find the next <code> node until the first non-<code> node. I used xpath here:

var nodes = doc.DocumentNode.SelectNodes(
    "//code[name(preceding-sibling::*[1])!='code']"
);
foreach (var node in nodes)
{
    var pre = HtmlNode.CreateNode("<pre class='brush: csharp'></pre>");
    node.ParentNode.InsertBefore(pre, node);
    var content = string.Empty;
    var next = node;
    do
    {
        content += next.InnerText + Environment.NewLine;
        var previous = next;
        next = next.SelectSingleNode("following-sibling::*[1][name()='code']");
        previous.Remove();
    } while (next != null);
    pre.AppendChild(doc.CreateTextNode(
        content.TrimEnd(Environment.NewLine.ToCharArray())
    ));
}

Answer 2

Sanitize the html you want to parse. HTML Agility Pack strip tags NOT IN whitelist