FastColoredTextBoxNS.InsertCharCommand.Undo C# (CSharp) Method

        public override void Undo()
        {
            ts.OnTextChanging();
            switch (c)
            {
                case '\n': MergeLines(sel.Start.iLine, ts); break;
                case '\r': break;
                case '\b':
                    ts.CurrentTB.Selection.Start = lastSel.Start;
                    char cc = '\x0';
                    if (deletedChar != '\x0')
                    {
                        ts.CurrentTB.ExpandBlock(ts.CurrentTB.Selection.Start.iLine);
                        InsertChar(deletedChar, ref cc, ts);
                    }
                    break;
                default:
                    ts.CurrentTB.ExpandBlock(sel.Start.iLine);
                    ts[sel.Start.iLine].RemoveAt(sel.Start.iChar);
                    ts.CurrentTB.Selection.Start = sel.Start;
                    break;
            }

            ts.NeedRecalc(new TextSource.TextChangedEventArgs(sel.Start.iLine, sel.Start.iLine));

            base.Undo();
        }