c# 清楚表格内容
ExcelWorksheet currentWorksheet = pck.Workbook.Worksheets[1];
//拷贝前一个sheet
currentWorksheet = pck.Workbook.Worksheets.Copy(currentsheetName, "currentWorksheet");
currentWorksheet.Cells["A2:C40000"].Clear(); // 拷贝的内容去掉