.net 时间的比较

  string  dbpath  =  Server.MapPath( " db/count.mdb " );
            DbAccess db  =   new  DbAccess(dbpath);
             #region  "添加"
             string  url  =  Convert.ToString(Request.UrlReferrer);
             string  ip   =  Convert.ToString(Request.UserHostAddress);

             // 判断
             string  sqlsel  =   string .Format( " select count(*) from record where ip='{0}' " ,ip);
             int  coun  =  Convert.ToInt32(db.GetDataTable(sqlsel).Rows[ 0 ][ 0 ].ToString());
             bool  add = false ;
             if (coun > 0 )
            {
                    sqlsel   =   string .Format( " select [date] from record where ip='{0}'order by date desc " ,ip);
                    DateTime dt  =  Convert.ToDateTime(db.GetDataTable(sqlsel).Rows[ 0 ][ " date " ].ToString());
                    DateTime now  =  DateTime.Now;
                    TimeSpan ts  =  now - dt;
                     double  time  =  ts.TotalHours;
                 if (time > 2 )
                {
                    add = true ;
                }
                 else
                {

                }
                    
            }
             else
            {
                add = true ;
            }
             // 添加
             if (add)
            {
         string  sqladd  =   string .Format( " insert into record(url,ip) values('{0}','{1}') " ,url,ip);
           
            db.ReturnState(sqladd);
            }
    
#endregion
             #region  显示
    
            DataSet ds  =   new  DataSet(); 
                ds = db.GetDataSet( " select count(*) from record " );
            
             this .coun = Convert.ToString(ds.Tables[ 0 ].Rows[ 0 ][ 0 ]);
             #endregion

    DateTime now  =  DateTime.Now;
            DateTime ot   =  DateTime.Now.AddDays( 3 );
             long   al  =  now.Ticks;
             long   ot1  =  ot.Ticks;
            Response.Write(al);
            Response.Write( " <br> " );
            Response.Write(ot1);
            Response.Write( " <br> " );
            Response.Write(ot1 - al);
            Response.Write( " <br> " );

            Response.Write(((ot1 - al) / 10000 / 1000 ) / ( 60 * 60 * 24 )); // 相差几天