FastColoredTextBoxNS.InsertCharCommand.InsertChar C# (CSharp) Method

        internal static void InsertChar(char c, ref char deletedChar, TextSource ts)
        {
            var tb = ts.CurrentTB;

            switch (c)
            {
                case '\n':
                    if (!ts.CurrentTB.AllowInsertRemoveLines)
                        throw new ArgumentOutOfRangeException("Cant insert this char in ColumnRange mode");
                    if (ts.Count == 0)
                        InsertLine(ts);
                    InsertLine(ts);
                    break;
                case '\r': break;
                case '\b'://backspace
                    if (tb.Selection.Start.iChar == 0 && tb.Selection.Start.iLine == 0)
                        return;
                    if (tb.Selection.Start.iChar == 0)
                    {
                        if (!ts.CurrentTB.AllowInsertRemoveLines)
                            throw new ArgumentOutOfRangeException("Cant insert this char in ColumnRange mode");
                        if (tb.LineInfos[tb.Selection.Start.iLine - 1].VisibleState != VisibleState.Visible)
                            tb.ExpandBlock(tb.Selection.Start.iLine - 1);
                        deletedChar = '\n';
                        MergeLines(tb.Selection.Start.iLine - 1, ts);
                    }
                    else
                    {
                        deletedChar = ts[tb.Selection.Start.iLine][tb.Selection.Start.iChar - 1].c;
                        ts[tb.Selection.Start.iLine].RemoveAt(tb.Selection.Start.iChar - 1);
                        tb.Selection.Start = new Place(tb.Selection.Start.iChar - 1, tb.Selection.Start.iLine);
                    }
                    break;
                case '\t':
                    int spaceCountNextTabStop = tb.TabLength - (tb.Selection.Start.iChar % tb.TabLength);
                    if (spaceCountNextTabStop == 0)
                        spaceCountNextTabStop = tb.TabLength;

                    for (int i = 0; i < spaceCountNextTabStop; i++)
                        ts[tb.Selection.Start.iLine].Insert(tb.Selection.Start.iChar, new Char(' '));

                    tb.Selection.Start = new Place(tb.Selection.Start.iChar + spaceCountNextTabStop, tb.Selection.Start.iLine);
                    break;
                default:
                    ts[tb.Selection.Start.iLine].Insert(tb.Selection.Start.iChar, new Char(c));
                    tb.Selection.Start = new Place(tb.Selection.Start.iChar + 1, tb.Selection.Start.iLine);
                    break;
            }
        }

        internal static void InsertText(string insertedText, TextSource ts)
        {
            var tb = ts.CurrentTB;

            try
            {
                tb.Selection.BeginUpdate();
                char cc = '\x0';

                if (ts.Count == 0)
                {
                    InsertCharCommand.InsertLine(ts);
                    tb.Selection.Start = Place.Empty;
                }
                tb.ExpandBlock(tb.Selection.Start.iLine);
                foreach (char c in insertedText)
                {
                    InsertCharCommand.InsertChar(c, ref cc, ts);
                }
                ts.NeedRecalc(new TextSource.TextChangedEventArgs(0, 1));
            }
            finally
            {
                tb.Selection.EndUpdate();
            }
        }