Question

public class News
{
    public virtual int Id { set; get; }
    public virtual string Title { get; set; }
    public virtual string Thumbnail { set; get; }
    public virtual string Image { set; get; }
    public virtual string NewsContent { set; get; }
    public virtual DateTime DateCreated { set; get; }
    public virtual bool Published { set; get; }
    public virtual int UserCreated { set; get; }
    public virtual Category Category { set; get; }
    public virtual DateTime DateUpdated { set; get; }
    public virtual int ViewCount { set; get; }
}

I have this class and I d like to query the database to get results. here is my query :

        foreach (var category in categories)
        {
            var news = newsRepo.Query("from News n where n.Category ="+category);
        }

here is the Query method.

    public IQueryable<T> Query(string query)
    {
        IQueryable<T> queryable;
        using (var session = SessionFactory.OpenSession())
        using (var transaction = session.BeginTransaction())
        {
            var hql = session.CreateQuery(query);
            var list = hql.List<T>();
            queryable = list.AsQueryable();
            transaction.Commit();
        }
        return queryable;
    }

and it doesnt work.

I get the following error:

could not execute query
[ select news0_.Id as Id13_, news0_.Title as Title13_, news0_.DateCreated as DateCrea3_13_, news0_.DateUpdated as DateUpda4_13_, news0_.NewsContent as NewsCont5_13_, news0_.Published as Published13_, news0_.UserCreated as UserCrea7_13_, news0_.Image as Image13_, news0_.Thumbnail as Thumbnail13_, news0_.ViewCount as ViewCount13_, news0_.Category_id as Category11_13_ from [News] news0_ where news0_.Category_id=. ]

How can i fix it?

any ideas?

Answer 1

If you put a break point at the following line of code then you should see that the category variable isn’t getting initialized to what you expect (which should be an integer):

var news = newsRepo.Query("from News n where n.Category ="+category);

That aside, there are several better ways of facilitating this query. One is to just use Session.Get(id) like so:

var news = Session.Get<News>(1);

You could also use the NHibernate LINQ provider like so:

var news = Session.Query<News>().SingleOrDefault();

Only use literal SQL or HQL when absolutely necessary.