NHibernate: Create iCriteria without session

Question

I want to construct ICriteria's and pass that on to a function. That function will open a session and transaction. Then the function executes the ICriteria.List(); and returns the list of objects, like the code below.

I want to do this because I only want to write using(ISession Session = ... and Using(ITransaction Transaction = ... once for collecting a list of objects. Otherwise I am repeating myself so many times.

    /// <summary>
    /// Executes a ICriterion in a new session using a transaction.
    /// </summary>
    /// <typeparam name="T">The type of object to operate on.</typeparam>
    /// <param name="Criterion">The criterion to get the list of objects by.</param>
    /// <returns>The result of <c>(List<T>)Session.CreateCriteria(typeof(T)).Add(Criterion).List()</c></returns>
    public static List<T> CriterionToList<T>(ICriterion Criterion)
    {
        List<T> Objects = default(List<T>);
        using (ISession Session = SessionFactory.OpenSession())
        {
            using (ITransaction Transaction = Session.BeginTransaction())
            {
                Objects = (List<T>)Session.CreateCriteria(typeof(T)).Add(Criterion).List<T>();
                Transaction.Commit();
            }
        }
        return Objects;
    }

The only thing ICriteria.Add() accepts is a ICriterion.

The Question

ICriterion does not have a .Add(.. So I can't do this:

ICriterion criterion = Restrictions.Eq(Property, Value).Add(...

How can I still achieve this, should I cast it to ICriteria first like so?

ICriterion criterion = ((ICriteria)Restrictions.Eq(Property, Value)).Add(...

NOTE: The problem is that I am converting a huge project that uses DataTables to strong typed objects (compatible with NHibernate). So I have many, many compile errors that prevents me from testing my code without converting the whole project first.

Answer 1

I think you can achieve this with DetachedCriteria. The syntax and usage would be like this:

var det = DetachedCriteria.For<T>.Add(Restrictions.Eq(prop, val));
using (var session = Config.OpenSession())
using (var txn = session.BeginTransaction())
{
    var result= det.GetExecutableCriteria(session).List();
}

You could easily encapsulate the transaction in a separate function:

public IList<T> GetList<T>(DetachedCriteria detachedCriteria)
{
    IList<T> result;
    using (var session = Config.OpenSession())
    using (var txn = session.BeginTransaction())
    {
        result = detachedCriteria.GetExecutableCriteria(session).List<T>();
        txn.Commit();
    }
    return result;
}