C# NPOI 把一个xlsx里的某sheet复制到另一个xlsx的问题

Question

            FileStream file2007Source = File.OpenRead("file2007Source.xlsx");
            FileStream file2007Target = new FileStream("file2007Target.xlsx", FileMode.OpenOrCreate);
            XSSFWorkbook f2s = new XSSFWorkbook(file2007Source);
            XSSFWorkbook f2t = new XSSFWorkbook(file2007Target);
            ISheet isheet = f2t.CreateSheet("testexp");
            for (int i = 0; i < f2s.GetSheetAt(0).LastRowNum; i++)
            {
                IRow irow = isheet.CreateRow(i);
                for (int j = 0; j < f2s.GetSheetAt(0).GetRow(i).LastCellNum; j++)
                {
                    ICell icell = irow.CreateCell(j);
                    icell.SetCellValue(f2s.GetSheetAt(0).GetRow(i).GetCell(j).ToString());
                }
            }
            file2007Source.Close();
            f2s.Close();
            file2007Target.Close();
            f2t.Close();

如代码所示，调试发现代码无语法错误但Target文件没有任何改变，无法实现提问的目的，求教哪里写错了。

Answer 1

using (FileStream fileStream = System.IO.File.Open(@"C:TempC.xlsx", FileMode.OpenOrCreate, FileAccess.ReadWrite))
{
f2s.Write(fileStream);
}