读取Excel模板，写入数据，并别输出另存为Excel文件

private void BtnExportExcelClick(object sender, EventArgs e)
        {
            var fromFileName = "D:/Excel/Book2.xls";
            var toFileName = "D:/Excel/Book3.xls";

            var saveFileDialog = new SaveFileDialog();

            saveFileDialog.Title = "保存";
            saveFileDialog.Filter = "Excel文档(*.xls)|*.xlsx";
            saveFileDialog.RestoreDirectory = true;
            if (saveFileDialog.ShowDialog() == DialogResult.OK)
            {
                toFileName = saveFileDialog.FileName;
            }
            

           
            Microsoft.Office.Interop.Excel._Application appExcel = new ApplicationClass();

            Microsoft.Office.Interop.Excel.Workbook workbook = appExcel.Workbooks.Open(fromFileName,
                     Type.Missing, Type.Missing, Type.Missing, Type.Missing,
                     Type.Missing, Type.Missing, Type.Missing, Type.Missing,
                     Type.Missing, Type.Missing, Type.Missing, Type.Missing,
                     Type.Missing, Type.Missing);//打开Excel

            //Workbook workbook = appExcel.Workbooks.Add(true);

            Worksheet xlsheet = (Worksheet)workbook.Worksheets[1];

            Range range = xlsheet.get_Range(appExcel.Cells[1, 1], appExcel.Cells[1, 1]);

            range.MergeCells = true;
            appExcel.ActiveCell.FormulaR1C1 = "这是Excel的标题";
            appExcel.ActiveCell.Font.Size = 20;
            appExcel.ActiveCell.Font.Bold = true;
            appExcel.ActiveCell.HorizontalAlignment = Microsoft.Office.Interop.Excel.Constants.xlCenter;

            //开始写入每列的标题 
            xlsheet.Cells[1,1] = "这是列的标题";

            //开始写入每列的数据 
            for (int i = 1; i < 30; i++)
            {
                xlsheet.Cells[i + 2, 1] = "这是列A"+i;
                xlsheet.Cells[i + 2, 2] = "这是列B" + i;
                xlsheet.Cells[i + 2, 3] = "这是列C" + i;
                xlsheet.Cells[i + 2, 4] = "这是列D" + i;
                xlsheet.Cells[i + 2, 5] = "这是列E" + i;
                xlsheet.Cells[i + 2, 6] = "这是列F" + i;
                xlsheet.Cells[i + 2, 7] = "这是列G" + i;
                xlsheet.Cells.ColumnWidth = 30;
            }
            

            workbook.Saved = true;
            workbook.SaveCopyAs(toFileName);

            workbook.Close();

            appExcel.Quit();
            GC.Collect();

            MessageBox.Show("[XXXXXXX]报表导出成功！","乐家购物",MessageBoxButtons.OK,MessageBoxIcon.Information);

        }