//记录当前区域第一行的行号（从0开始的）
            Point pos = new Point(0, 0);
            int firstIndex = richTextBox1.GetCharIndexFromPosition(pos);
            int firstLine = richTextBox1.GetLineFromCharIndex(firstIndex);
           


            //根据保存的行号确定滚动条
            int line = 11;//滚动到第11行 （firstLine+1）
              int start = this.richTextBox1.GetFirstCharIndexFromLine(line);
            this.richTextBox1.SelectionStart = start;
            this.richTextBox1.ScrollToCaret();