Question

Utilizing NHibernate I am attempting to use a lambda expression to retrieve objects based on the status and values between a parent child relationship. AbstractWorkflowRequestInformation has a collection of WorkflowRequestInformationAction. Each of the two classes have their own Status properties. To illustrate here are the abbreviated classes as they relate to this query:

public class AbstractWorkflowRequestInformation
{
    public virtual RequestStatus RequestStatus { get; set; }

    public virtual IEnumerable<WorkflowRequestInformationAction>
        WorkflowRequestInformationActionList { get; set; }
}

public class WorkflowRequestInformationAction
{
    public virtual ActionStatus Status { get; set; }

    public virtual string RoleIdentifier { get; set; }

    public virtual string RoleName { get; set; }
}

Given this relationship I want to retrieve AbstractWorkflowRequestInformation objects based on a List<KeyValuePair<string, string>> called roles. I realize that the exception is being caused by a lack of parsing of the Any(...) extension method, but I am unsure of alternative queries. Thus far all permutations on the below query have caused the same or similar exceptions:

public IEnumerable<IRequestInformation> GetRequestsPendingActionBy(
        List<KeyValuePair<string, string>> roles)
{
    var results = GetSession().Query<AbstractWorkflowRequestInformation>()
        .Where(r => r.RequestStatus == RequestStatus.Pending
                    && r.WorkflowRequestInformationActionList
                        .Any(a => ActionStatus.Pending == a.Status
                                  && roles.Any(kp => kp.Key == a.RoleName
                                               && kp.Value == a.RoleIdentifier)))
    .ToList();

    return results;
}

The ultimate goal is to retrieve only those AbstractWorkflowRequestInformation objects which are pending and have a pending WorkflowRequestInformationAction matching a KeyValuePair in the roles enumerable.

I am not wedded to using a lambda expression as this expression has already grown unwieldy, if there’s a more elegant ICriteria expression I am all ears. What are my options to restrict my results based upon the values in my roles List<KeyValuePair<string, string>> but prevent the “Specified method is not supported” exception?

Answer 1

I think this would get same results…

WorkflowRequestInformationAction actionAlias = null;

var q = GetSession().QueryOver<AbstractWorkflowRequestInformation>()
    .Inner.JoinAlias(x => x.WorkflowRequestInformationActionList,
                          () => actionAlias)
    .Where(x => x.RequestStatus == RequestStatus.Pending)
    .And(() => actionAlias.Status == ActionStatus.Pending);

var d = Restrictions.Disjunction();

foreach(var kvp in roles) 
{
    d.Add(Restrictions.Where(() => actionAlias.RoleName == kvp.Key
                                  && actionAlias.RoleIdentitifier == kvp.Value));
}

q.And(d).TransformUsing(Transformers.DistinctRootEntity);

var results = q.List();

You could probably take a similar approach with NH Linq. I’m more comfortable with QueryOver/Criteria though.