NPOI合并单元格后的边框设置

通过NPOI将单元格B2-C3进行单元格合并，并添加边框。一开始我的写法是这样的：

        static void Main(string[] args)
        {
            HSSFWorkbook workbook = new HSSFWorkbook();
            HSSFSheet sheet = workbook.CreateSheet("Sheet1") as HSSFSheet;
            HSSFRow dataRow = sheet.CreateRow(1) as HSSFRow;
            dataRow = sheet.CreateRow(1) as HSSFRow;
            CellRangeAddress region = new CellRangeAddress(1, 2, 1, 2);
            sheet.AddMergedRegion(region);
            ICell cell = dataRow.CreateCell(1);
            cell.SetCellValue("test");

            ICellStyle style = workbook.CreateCellStyle();
            style.BorderBottom = BorderStyle.Thin;
            style.BorderLeft = BorderStyle.Thin;
            style.BorderRight = BorderStyle.Thin;
            style.BorderTop = BorderStyle.Thin;
            style.BottomBorderColor = HSSFColor.Black.Index;
            style.LeftBorderColor = HSSFColor.Black.Index;
            style.RightBorderColor = HSSFColor.Black.Index;
            style.TopBorderColor = HSSFColor.Black.Index;

            cell.CellStyle = style;


            using (MemoryStream ms = new MemoryStream())
            {
                workbook.Write(ms);
                ms.Flush();
                ms.Position = 0;
                using (FileStream fs = new FileStream("C:\\TestConsole.xls", FileMode.Create, FileAccess.Write))
                {
                    byte[] data = ms.ToArray();
                    fs.Write(data, 0, data.Length);
                    fs.Flush();
                }
            }
        }

但输出的结果却是这样的：

由此可见NPOI还是认为我Create的Cell是B2，但由于合并后，右侧和下部边框不存在了，产生了以上的结果。

我的解决方案是对合并区域的所有单元格遍历设置边框，代码如下

        static void Main(string[] args)
        {
            HSSFWorkbook workbook = new HSSFWorkbook();
            HSSFSheet sheet = workbook.CreateSheet("Sheet1") as HSSFSheet;
            HSSFRow dataRow = sheet.CreateRow(1) as HSSFRow;
            dataRow = sheet.CreateRow(1) as HSSFRow;
            CellRangeAddress region = new CellRangeAddress(1, 2, 1, 2);
            sheet.AddMergedRegion(region);
            ICell cell = dataRow.CreateCell(1);
            cell.SetCellValue("test");

            ICellStyle style = workbook.CreateCellStyle();
            style.BorderBottom = BorderStyle.Thin;
            style.BorderLeft = BorderStyle.Thin;
            style.BorderRight = BorderStyle.Thin;
            style.BorderTop = BorderStyle.Thin;
            style.BottomBorderColor = HSSFColor.Black.Index;
            style.LeftBorderColor = HSSFColor.Black.Index;
            style.RightBorderColor = HSSFColor.Black.Index;
            style.TopBorderColor = HSSFColor.Black.Index;

            //cell.CellStyle = style;
            for (int i = region.FirstRow; i <= region.LastRow; i++)
            {
                IRow row = HSSFCellUtil.GetRow(i, sheet);
                for (int j = region.FirstColumn; j <= region.LastColumn; j++)
                {
                    ICell singleCell = HSSFCellUtil.GetCell(row, (short)j);
                    singleCell.CellStyle = style;
                }
            }

            using (MemoryStream ms = new MemoryStream())
            {
                workbook.Write(ms);
                ms.Flush();
                ms.Position = 0;
                using (FileStream fs = new FileStream("C:\\TestConsole.xls", FileMode.Create, FileAccess.Write))
                {
                    byte[] data = ms.ToArray();
                    fs.Write(data, 0, data.Length);
                    fs.Flush();
                }
            }
        }

检查结果：

大功告成。