The code below works correctly with the example provided, even deals with some weird stuff like <div><br></div>, there’re still some things to improve, but the basic idea is there. See the comments.
public static string FormatLineBreaks(string html)
{
//first - remove all the existing '\n' from HTML
//they mean nothing in HTML, but break our logic
html = html.Replace("\r", "").Replace("\n", " ");
//now create an Html Agile Doc object
HtmlDocument doc = new HtmlDocument();
doc.LoadHtml(html);
//remove comments, head, style and script tags
foreach (HtmlNode node in doc.DocumentNode.SafeSelectNodes("//comment() | //script | //style | //head"))
{
node.ParentNode.RemoveChild(node);
}
//now remove all "meaningless" inline elements like "span"
foreach (HtmlNode node in doc.DocumentNode.SafeSelectNodes("//span | //label")) //add "b", "i" if required
{
node.ParentNode.ReplaceChild(HtmlNode.CreateNode(node.InnerHtml), node);
}
//block-elements - convert to line-breaks
foreach (HtmlNode node in doc.DocumentNode.SafeSelectNodes("//p | //div")) //you could add more tags here
{
//we add a "\n" ONLY if the node contains some plain text as "direct" child
//meaning - text is not nested inside children, but only one-level deep
//use XPath to find direct "text" in element
var txtNode = node.SelectSingleNode("text()");
//no "direct" text - NOT ADDDING the \n !!!!
if (txtNode == null || txtNode.InnerHtml.Trim() == "") continue;
//"surround" the node with line breaks
node.ParentNode.InsertBefore(doc.CreateTextNode("\r\n"), node);
node.ParentNode.InsertAfter(doc.CreateTextNode("\r\n"), node);
}
//todo: might need to replace multiple "\n\n" into one here, I'm still testing...
//now BR tags - simply replace with "\n" and forget
foreach (HtmlNode node in doc.DocumentNode.SafeSelectNodes("//br"))
node.ParentNode.ReplaceChild(doc.CreateTextNode("\r\n"), node);
//finally - return the text which will have our inserted line-breaks in it
return doc.DocumentNode.InnerText.Trim();
//todo - you should probably add "&code;" processing, to decode all the and such
}
//here's the extension method I use
private static HtmlNodeCollection SafeSelectNodes(this HtmlNode node, string selector)
{
return (node.SelectNodes(selector) ?? new HtmlNodeCollection(node));
}