change the font for richtextbox uxing C #

Please try the following and let me know if it works

            // Set title style
            rtb.SelectionColor = Color.Blue;
            rtb.SelectionFont = new Font("Calibri", 12, FontStyle.Bold);
            
            rtb.SelectedText += "Title: " + rssChannel.GetString("title") + " \r\n";

            // Set remaining style
            rtb.SelectionColor = Color.Black;
            rtb.SelectionFont = new Font("Calibri", 10, FontStyle.Regular);

            rtb.SelectedText += "Description: " + rssChannel.GetString("description") + "\r\n";
            rtb.SelectionColor = Color.Black;

            rtb.SelectionFont = new Font("Calibri", 10, FontStyle.Regular);
            rtb.SelectedText += "Link: " + rssChannel.GetString("link") + "\r\n";