C# Excel复制格式问题

                Microsoft.Office.Interop.Excel.Workbook result = app.Workbooks.Add(Excel.XlWBATemplate.xlWBATWorksheet);

                Microsoft.Office.Interop.Excel.Workbook wb1 = app.Workbooks.Open(Path.GetFullPath(@lastfiledir1), 0, true, 5, "", "", false, Excel.XlPlatform.xlWindows, "", true,

                                                  false, 0, true, false, false);

                Microsoft.Office.Interop.Excel.Workbook wb2 = app.Workbooks.Open(Path.GetFullPath(@lastfiledir2), 0, true, 5, "", "", false, Excel.XlPlatform.xlWindows, "", true,

                                                  false, 0, true, false, false);



                Excel.Worksheet targetSheet = (Excel.Worksheet)result.Worksheets[1];

                int currentRow = 1;//假设目标表原来是空白的

                Excel.Range targetRng = targetSheet.get_Range(targetSheet.Cells[currentRow, 1], targetSheet.Cells[currentRow, 1]);



                //复制第一张表的内容

                Excel.Worksheet sheet = (Excel.Worksheet)wb1.Worksheets[1];

                Excel.Range rng = sheet.UsedRange;

                rng.Copy(targetRng);

                if (rng.Value == null) { }

                currentRow = targetSheet.UsedRange.Rows.Count + 1;

                targetRng = targetSheet.get_Range(targetSheet.Cells[currentRow, 1], targetSheet.Cells[currentRow, 1]);

                //复制第二张表的内容

                sheet = (Excel.Worksheet)wb2.Worksheets[1];

                rng = sheet.UsedRange.get_Offset(1, 0);//重复的标题行舍掉

                rng.Copy(targetRng);



                targetRng.Font.Name = "宋体";

                targetRng.Font.Size = 8;

                targetRng.HorizontalAlignment = Excel.XlVAlign.xlVAlignCenter;