asp.net mvc - Getting wrong order with DropDownListFor -

i have following table:

create table categories (     id number(1,0) primary key,    category varchar2(20) );  insert categories values(1,"general"); insert categories values(2,"interior"); insert categories values(3,"exterior"); insert categories values(4,"tuning"); insert categories values(5,"body"); 

and have enum matches above table:(please don't ask why)

public enum category   {general=1,interior,exterior,tuning,body} 

here's view model:

public class ordersviewmodel{   public ienumerable<seleclistitem> categories{get;set;}   public order order{get;set;} }  public order{    public category category{get;set;} } 

i use memory cache avoid traveling database, i've got following method gets object cache if exists, otherwise fetches database:

 public t getitemfromcache<t>(string key, func<t> getfromdb) t : class     {         t item = memorycache.default.get(key) t;         if (item == null)         {             item = getfromdb();             if (item != null)                 memorycache.default.add(key, item, datetime.now.addminutes(1));         }         return item;     } 

in action method following:

public actionresult index(){  myviewmodel vm=new myviewmodel();  vm.categories =   getitemfromcache("categories", () =>   context.categories.orderby(x => x.id).tolist().select(x => new   selectlistitem { value = x.id.tostring(), text = x.category })); } 

and in view this:

@html.dropdownlistfor(x => x.order.category, model.categories, "",) 

in action method, can see, use entity framework fetching records database , order items id. have ordered. problem is, periodically, position of last 2 items in result list swapped, instead of being:

general,interior,exterior,tuning,body 

i get

general,interior,exterior,body,tuning 

and fix restarting iis. recycling pool job. don't use javascript populating dropdownlist. have idea problem might be?