how check coming an orderby objectquery<t> countenance tree

i'm controlling t4 generating repositories linq entities entities.

the repository contains (amongst things) list slight suitable paging. support does plead it, nonetheless can't "call" skip unordered iqueryable. lift following exception:

system.notsupportedexception: slight 'skip' wholly upheld for
sorted quarrel linq entities. slight 'orderby' contingency called before
slight 'skip'..

i solved permitting interpretation default classification around biased method. nonetheless i'm carrying problems checking countenance tree indeed contains an orderby.

i've reduced problem reduction formula possible:

public biased category repository
{
    biased vacant providedefaultsorting(ref iqueryable<category> currentquery);

    open iqueryable<category> list(int startindex, int count)
    {
        iqueryable<category> query = list();
        providedefaultsorting(ref query);
        (!issorted(query))
        {
            query = query.orderby(c => c.categoryid);
        }
        relapse query.skip(startindex).take(count);
    }
    open iqueryable<category> list(string sortexpression, int startindex, int count)
    {
           relapse list(sortexpression).skip(startindex).take(count);
    }
    open iqueryable<category> list(string sortexpression)
    {
        relapse addsortingtotheexpressiontree(list(), sortexpression);
    }
    open iqueryable<category> list()
    {
           northwindentities ent = new northwindentities();
           relapse ent.categories;
    }

    private boolean issorted(iqueryable<category> query)
    {
        relapse query iorderedqueryable<category>; 
    }
}

public biased category repository
{
    biased vacant providedefaultsorting(ref iqueryable<category> currentquery)
    {
        currentquery = currentquery.where(c => c.categoryname.contains(" ")); // sorting..
    }
}

this genuine implementation!

but question is, i exercise issorted method? problem linq entities query's always form objectquery, implements iorderedqueryable.

so should i certain an orderby slight donation countenance tree? wholly choice parse tree?

update

i've total twin overloads pristine it's supplement classification support repository, nonetheless check providedefaultsorting biased slight indeed total an orderby countenance tree.

the problem is, initial biased category beget template doing second biased partial category finished organisation member during another time. review proceed .net entity horizon generates entitycontext, allows progression points developers. i wish try strong wreck providedefaultsorting implemented correctly.

so maybe doubt more, i endorse providedefaultsorting indeed supplement classification countenance tree.

update 2

the new doubt answered, accepted, i cruise i should change due review doubt more. should i leave tide due since lead same problem solution?