How to add dynamic sort by direction to NHibernate queryover

Question

I am trying to add dynamic order by direction to my nhibernate queryover. Can anyone help how to do this? I was able to add dynamic orderby field. but dont know how to do the order by direction. Please find below my code:

    if (!string.IsNullOrEmpty(sortField))
    {
        var sortByProperty = Helper.GetSortByProperty(sortField);
        if (sortByProperty != null)
        {
            query.OrderBy(x => sortByProperty.GetValue(x, null));
        }
    }

    var result = query.Skip(pageIndex*pageSize)
                        .Take(pageSize)
                        .Future<Member>();

Answer 1

The way I have done this is, passing in a ListSortDirection type variable to the function that is doing the query.

So then you could apply the

• OrderBy() which:

Sorts the elements of a sequence in ascending order according to a key.

• OrderByDescending() which:

Sorts the elements of a sequence in descending order according to a key.

on your IQueryable<T> depending on the values from ListSortDirection.Ascending or ListSortDirection.Descending.

---

As requested by OP in comments, added sample generic code:

public IList<T> GetEntityList<T>(Expression<Func<T, bool>> whereExpression, Expression<Func<T, object>> orderByExpression, ListSortDirection orderDirection, int totalPages, int start, int limit)
{
    IList<T> returnVar;
    using (var session = _nhibernate.OpenSession())
    {
        var firstQueryable = session.Query<T>().Where(whereExpression);

        IQueryable<T> secondQueryable = orderDirection == ListSortDirection.Ascending ? firstQueryable.OrderBy(orderByExpression) : firstQueryable.OrderByDescending(orderByExpression);

        returnVar = totalPages > 0 ? secondQueryable.Skip(start).Take(limit).ToList() : secondQueryable.ToList();    
    }

    return returnVar;
}

---

To address another question in comment from OP, for the QueryOver API, for instance you can use the .OrderBy(orderByExpression).Desc for reverse sorting.