Is there a way to replace html nodes with text nodes using HTMLAgilityPack?

I would like to use HTMLAgility pack to replace a node within the document with a text node. The purpose of this is to remove tags surrounding the node itself. Currently, I do something like this:

//This code fixes redundant HTML formatting tags
//This is a snippet of code
foreach (var hChildNode in hd.DocumentNode.SelectNodes("//b//b | //i//i | //u//u") ?? Enumerable.Empty<HtmlNode>())
    hChildNode.Name = "remove";
StringBuilder sb = new StringBuilder(hd.DocumentNode.WriteTo());
sb.Replace("<remove>", string.Empty);
sb.Replace("</remove>", string.Empty);

Is there a better way to do this? If I try to create a new text node, and then do something like the code snippet below, I receive an invalid cast error:

foreach (var hChildNode in hd.DocumentNode.SelectNodes("//b//b | //i//i | //u//u") ?? Enumerable.Empty<HtmlNode>())
{
    HtmlNode hNewNode = hd.CreateTextNode(hChildNode.InnerHtml);
    hChildNode.ParentNode.ReplaceChild(hNewNode, hChildNode);
}

(updated after a typo was pointed out, however the problem still remains)

Am I using the method wrong? Is there another method I am supposed to use to perform functions like this? Thanks.