Cannot convert Linq.IOrderedEnumerable<T> to Linq.IQueryable<T>

Question

Trying to add an orderby statement to my generic repository method and getting the below error. Not sure why as it seems I am able to add a .OrderBy to an IQueryable in other cases.

What am I missing?

Getting Error:

Cannot implicitly convert type 'System.Linq.IOrderedEnumerable' to 'System.Linq.IQueryable'

Code Snippet (some parts removed):

public class QuickbooksRespository<TEntity>
         where TEntity : class, Intuit.Ipp.Data.IEntity, new()
    {
    public virtual IQueryable<TEntity> GetAll(
        int page, int pageSize,
        Func<TEntity, object> orderbyascending = null,
        Func<TEntity, object> orderbydescending = null)
    {
        int skip = Math.Max(pageSize * (page - 1), 0);

        IQueryable<TEntity> results = _qbQueryService
                .Select(all => all);

        if (orderbyascending != null)
        {
            results = results.OrderBy(orderbyascending);
        }

        if (orderbydescending != null)
        {
            results = results.OrderByDescending(orderbydescending);
        }

        return results
                .Skip(skip)
                .Take(pageSize);
    }
}

Answer 1

Because you're providing Func<...> delegate, IEnumerable.OrderBy extension method is chosen. Change your method parameters to Expression<Func<...>>:

public virtual IQueryable<TEntity> GetAll(
    int page, int pageSize,
    Expression<Func<TEntity, object>> orderbyascending = null,
    Expression<Func<TEntity, object>> orderbydescending = null)

It will make IQueryable.OrderBy() method to be choose instead of IEnumerable.OrderBy() when you actually call OrderBy() later.