FastColoredTextBoxNS.ReplaceTextCommand.Undo C# (CSharp) Method

        public override void Undo()
        {
            var tb = ts.CurrentTB;

            ts.OnTextChanging();
            tb.BeginUpdate();

            tb.Selection.BeginUpdate();
            for (int i = 0; i<ranges.Count; i++)
            {
                tb.Selection.Start = ranges[i].Start;
                for (int j = 0; j < insertedText.Length; j++)
                    tb.Selection.GoRight(true);
                ClearSelected(ts);
                InsertTextCommand.InsertText(prevText[prevText.Count - i - 1], ts);
            }
            tb.Selection.EndUpdate();
            tb.EndUpdate();

            if (ranges.Count > 0)
                ts.OnTextChanged(ranges[0].Start.iLine, ranges[ranges.Count - 1].End.iLine);

            ts.NeedRecalc(new TextSource.TextChangedEventArgs(0, 1));
        }