Excel.Application ThisApp = new Excel.ApplicationClass();
   Excel.Workbooks ThisWbs = ThisApp.Workbooks;
   Excel.Workbook ThisWb = ThisWbs.Open("G:/demo.xls",Missing.Value,Missing.Value,Missing.Value,Missing.Value,Missing.Value,Missing.Value,Missing.Value,Missing.Value,Missing.Value,Missing.Value,Missing.Value,Missing.Value,Missing.Value,Missing.Value);
   ThisWb.SaveAs("G:/HelloExcel.xml",Excel.XlFileFormat.xlXMLSpreadsheet,Missing.Value,Missing.Value,Missing.Value,Missing.Value,Excel.XlSaveAsAccessMode.xlNoChange,Missing.Value,Missing.Value,Missing.Value,Missing.Value,Missing.Value);
//Excel.XlFileFormat.xlXMLSpreadsheet控制存储文件的类型
   System.Runtime.InteropServices.Marshal.ReleaseComObject(ThisWb);
   ThisWb = null;
   ThisWbs.Close();
   System.Runtime.InteropServices.Marshal.ReleaseComObject(ThisWbs);
   ThisWbs = null;
   System.Runtime.InteropServices.Marshal.ReleaseComObject(ThisApp);
   ThisApp = null;
   GC.Collect();