Nhibernate query to select count of grouped by rows - nhibernate

Question

I need to get this query using NHibernate:
Select RequestStatus.[Status], Count(ApprovalRequest.Id)
From ApprovalRequest Inner Join RequestStatus On ApprovalRequest.CurrentStatusId = RequestStatus.Id
Where RequestStatus.[Status] In ('Approved', 'Queried') And ApprovalRequest.Deleted != 1
Group By RequestStatus.[Status]
here are my classes:
public class ApprovalRequest
{
public ApprovalRequest()
{
Id = Guid.NewGuid();
Statuses = new List<RequestStatus>();
}
/// <summary>
/// Identity No.
/// </summary>
public Guid Id { get; set; }
/// <summary>
/// Represents the current status of the request e.g. Approved.
/// </summary>
public RequestStatus CurrentStatus { get; set; }
/// <summary>
/// The statuses that the request experiences.
/// </summary>
public IList<RequestStatus> Statuses { get; set; }
}
}
public class RequestStatus
{
public RequestStatus()
{
Id = Guid.NewGuid();
}
public Guid Id { get; set; }
public StatusEnum Status { get; set; }
}
I tried this query :
var lst = uow.Session.QueryOver<ApprovalRequest>()
.JoinQueryOver<RequestStatus>(req => req.CurrentStatus)
.SelectList(list =>
list
.SelectCount(p => p.Id)
.SelectGroup(p => p.CurrentStatus.Status)
).List();
but I got an error:
could not resolve property: CurrentStatus.Status of: ApprovalRequest (NHibernate)

Answer 1

You need to bind your joined table to an alias.
ApprovalRequest approvalRequestAlias = null;
RequestStatus requestStatusAlias = null;
var lst = uow.Session.QueryOver<ApprovalRequest>(() => approvalRequestAlias)
.JoinAlias(() => approvalRequestAlias.CurrentStatus, () => requestStatusAlias)
.SelectList(list => list
.SelectCount(p => p.Id)
.SelectGroup(p => requestStatusAlias.Status)
).List();