Mike Sampson: Inside Rev9

Bug tracking system for ... you know ... bugs

QueryFactory is actually very simple

namespace Channel9Controller.Infrastructure 
{ 
    public class QueryFactory : IQueryFactory 
    { 
        private readonly IUnityContainer container; 
        public QueryFactory(IUnityContainer container) 
        {
            this.container = container; 
        } 
        public TQueryType Create<TQueryType>() where TQueryType : IQuery 
        { 
            TQueryType query = container.Resolve<TQueryType>(); 
            query.EnableCaching(); 
             return query; 
        } 
    } 
}

The trick is that every query takes an NHibernate ISession that it uses to do its work. I have that session delivered up by the Unity container so all the Query has to do is specify that it needs ISession by taking one it its constructor and it gets the session for this request. Queries can also take addition parameters if they need. Most don't need any but some need to do operations based on when Now is so they take an IClock which is a simple interface that has a single property Now. I use this instead of DateTime.Now to make things easier to test and to ensure that time is tightly controlled in the application. I even have a specialty clock that returns Now as the most recently passed 5 minute mark (10:00, 10:05, etc). I use this for checking things like Published on an Entry or Banned on a user so that the query will cache better.