test.cs

public static void CompareAndApplyStyle(
   this TXTextControl.TextControl textControl, 
   string paragraphStyleName) {

   // store input position
   var iStartPos = textControl.Selection.Start;

   // retrieve the style based on a name
   TXTextControl.ParagraphStyle style = 
      textControl.ParagraphStyles.GetItem(paragraphStyleName);

   // loop through all paragraphs to check whether the style
   // matches the paragraph style
   foreach (TXTextControl.Paragraph par in textControl.Paragraphs) {

      textControl.Select(par.Start, 0);
      var selection = textControl.Selection;

      if (selection.Baseline == style.Baseline &&
         selection.Bold == style.Bold &&
         selection.FontName == style.FontName &&
         selection.FontSize == style.FontSize &&
         selection.ForeColor == style.ForeColor &&
         selection.Italic == style.Italic &&
         selection.Strikeout == style.Strikeout &&
         selection.Underline == style.Underline) {

         // style matches - apply style
         par.FormattingStyle = paragraphStyleName;
      }

   }

   // reset input position
   textControl.Selection.Start = iStartPos;
}