How to Highlight a specific word in WebBrowser control C#

you're going to need to import the Microsoft.mshtml assembly reference if you haven't already, and add

using mshtml;

        if (webBrowser1.Document != null)
        {
            IHTMLDocument2 document = webBrowser1.Document.DomDocument as IHTMLDocument2;
            if (document != null)
            {
                IHTMLBodyElement bodyElement = document.body as IHTMLBodyElement;
                if (bodyElement != null)
                {
                    IHTMLTxtRange trg = bodyElement.createTextRange();


                    if (trg != null)
                    {
                        const String SearchString = "Privacy"; // This is the search string you're looking for.
                        const int wordStartOffset = 421; // This is the starting position in the HTML where the word you're looking for starts at.
                        int wordEndOffset = SearchString.Length;
                        trg.move("character", wordStartOffset);
                        trg.moveEnd("character", wordEndOffset);

                        trg.select();
                    }
                }
            }
        }

here is a snippet that might be helpful also:

        if (webBrowser1.Document != null)
        {
            IHTMLDocument2 document = webBrowser1.Document.DomDocument as IHTMLDocument2;
            if (document != null)
            {
                IHTMLSelectionObject currentSelection = document.selection;

                IHTMLTxtRange range = currentSelection.createRange() as IHTMLTxtRange;
                if (range != null)
                {
                   const String search = "Privacy";

                   if (range.findText(search, search.Length, 2))
                   {
                       range.select();
                   }
                }
            }
        }

I am a novice programmer is my best samples. Just spend a lot of time.

Just connect your library

Project - add a link - Overview - windows - system32 - mshtml.tlb

using mshtml;

  private void button1_Click(object sender, EventArgs e)
    {

    webBrowser1.Refresh();

        Application.DoEvents();

        if (webBrowser1.Document != null)
        {

            IHTMLDocument2 document = webBrowser1.Document.DomDocument as IHTMLDocument2;
            if (document != null)
            {
                IHTMLSelectionObject currentSelection = document.selection;

                IHTMLTxtRange range = currentSelection.createRange() as IHTMLTxtRange;

                if (range != null)
                {
                    String search = textBox1.Text;
                    if (search == "")
                    {
                        MessageBox.Show("not selected");                          
                    }
                    else
                    {
                    line1:
                        if ((range.findText(search)) && (range.htmlText != "span style='background-color: rgb(255, 255, 0);'>" + textBox1.Text + "</span>"))
                        {
                            range.select();
                            range.pasteHTML("<span style='background-color: rgb(255, 255, 0);'>" + textBox1.Text.ToLower() + "</span>");
                            goto line1;

                        }
                    }

                }
            }
        }
      }