Entity Framework Order by descending by row field in query

I want to write a EF query which does order by ascending or descending based on condition. Following is the my pseudo code:

  var result= q.OrderByDescending(x => x.StatusId == 3)
                    then if( x.StatusId == 3) 
                          then order by x.ReserveDate
                     else
                          then order by descending x.LastUpdateDate

How can i do this?