利用NPOI修改Excel文件

private void button6_Click(object sender, EventArgs e)
{
//string FileName = @"D:Excel2007-1019.xlsx";
string FileName = @"D:Excel2003-1102.xls";

if (!File.Exists(FileName))
{
return;
}

if (
(FileName.ToUpper().IndexOf(".xlsx".ToUpper()) < 0)
&& (FileName.ToUpper().IndexOf(".xls".ToUpper()) < 0)
)
{
return;
}

IWorkbook wk = null;
using (FileStream fs = File.Open(FileName, FileMode.OpenOrCreate, FileAccess.Read, FileShare.ReadWrite))
{
if (FileName.ToUpper().IndexOf(".xlsx".ToUpper()) > 0)
{
wk = new XSSFWorkbook(fs);
}
else
{
wk = new HSSFWorkbook(fs);
}
}

ISheet sheet = wk.GetSheetAt(0);
if (wk.GetSheetAt(0) == null)
{
sheet = wk.CreateSheet();
}

// 在现有行的下面添加一些数据
int startRow = sheet.LastRowNum + 1;

IRow row = sheet.CreateRow(startRow);
row.CreateCell(0).SetCellValue("创建时间：" + DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss.fff"));
row.CreateCell(1).SetCellValue("中");
row.CreateCell(2).SetCellValue("国");
row.CreateCell(3).SetCellValue("南");
row.CreateCell(4).SetCellValue("海");

using (FileStream fileStream = File.Open(FileName, FileMode.OpenOrCreate, FileAccess.ReadWrite))
{
wk.Write(fileStream);
}

}