Question

I’ve been struggling a bit with this tiny problem – and I’m quite sure there’s an “easy” solution.

I have a generic nHibernate base-repository class with the following method:

public IList<T> GetAll()
{
    using (var session = SessionProvider.OpenSession())
    {
        return session.Query<T>().ToList();
    }
}

However – I’m trying to control my model by using some very simple interfaces. I have an interface – ISetDeleted:

public interface ISetDeleted
{
    bool Deleted { get; set; }
}

In my GetAll()-method I would like to check it the current type implements this interface – and if it does, only return the entities that are not marked as deleted:

public IList<T> GetAll()
{
    using (var session = SessionProvider.OpenSession())
    {
        if (typeof(T) is ISetDeleted)
        {
            // Only retrieve entities that are not marked as deleted
            // WHAT DO I DO HERE?
        }
        return session.Query<T>().ToList();
    }
}

I know I could just retrieve all the entities and loop through these – but I would prefer a cleaner approach – e.g. an expression that implements the check (if possible).

It would be very much appreciated if someone could help me out with this 🙂

Answer 1

First

typeof(T) is ISetDeleted

will only return true if the type parameter is ISetDeleted, not if it implements the interface. You probably want

if (typeof(ISetDeleted).IsAssignableFrom(typeof(T)))

Second, I think you want

return session.Query<T>().Where(x => !((ISetDeleted)x).IsDeleted).ToList();