Excel.ApplicationClass excel=new Microsoft.Office.Interop.Excel.ApplicationClass();
   Type excelType=excel.GetType();
   Excel.Workbooks workbooks=excel.Workbooks;

   excel.Visible=true;
   // 打开文件
   Type workbooksType=workbooks.GetType();
   object temp="c:\\test.xlt";
   Excel.Workbook workbook=(Excel.Workbook)workbooksType.InvokeMember("Add",System.Reflection.BindingFlags.InvokeMethod,null,workbooks,new object[]{temp});
 }