问题
I want to use query over to give me back an object
public class TaskMap : ClassMap<Task>
{
public TaskMap()
{
Table("Tasks");
Id(x => x.TaskId);
Map(x => x.TaskName).NvarcharWithMaxSize().Not.Nullable();
Map(x => x.Description).NvarcharWithMaxSize();
Map(x => x.DueDate).Not.Nullable();
HasMany(x => x.PersonalTaskReminders).Inverse();
HasMany(x => x.TaskReminders).Inverse();
References(x => x.Course).Not.Nullable();
HasMany(x => x.CompletedTasks);
}
}
[Serializable()]
public class Task
{
public virtual int TaskId { get; private set; }
public virtual string TaskName { get; set; }
public virtual string Description { get; set; }
public virtual DateTime DueDate { get; set; }
public virtual IList<PersonalTaskReminder> PersonalTaskReminders { get; set; }
public virtual IList<TaskReminder> TaskReminders { get; set; }
public virtual IList<CompletedTask> CompletedTasks { get; set; }
public virtual Course Course { get; set; }
public Task()
{
PersonalTaskReminders = new List<PersonalTaskReminder>();
TaskReminders = new List<TaskReminder>();
CompletedTasks = new List<CompletedTask>();
}
}
public class PlannerTask
{
public int TaskId { get; set; }
public string TaskName { get; set; }
public string Description { get; set; }
public DateTime DueDate { get; set; }
public List<PersonalTaskReminder> PersonalTaskReminders { get; set; }
public List<TaskReminder> TaskReminders { get; set; }
public Course Course { get; set; }
public bool IsCompleted { get; set; }
}
Try 1
Task tAlias = null;
PlannerTask plannerTask = null;
List<PlannerTask> result = session.QueryOver<Task>(() => tAlias)
.Select(x => x.Course).TransformUsing(Transformers.AliasToBean<PlannerTask>())
.List<PlannerTask>().ToList();
result: 188 records with all null for course object.
Try 2
Task tAlias = null;
PlannerTask plannerTask = null;
List<PlannerTask> result = session.QueryOver<Task>(() => tAlias)
.Select(Projections.Property(() => tAlias.TaskId).WithAlias(() => plannerTask.TaskId),
Projections.Property(() => tAlias.TaskName).WithAlias(() => plannerTask.TaskName),
Projections.Property(() => tAlias.DueDate).WithAlias(() => plannerTask.DueDate),
Projections.Property(() => tAlias.Description).WithAlias(() => plannerTask.Description),
Projections.Property(() => tAlias.PersonalTaskReminders).WithAlias(() => plannerTask.PersonalTaskReminders),
Projections.Property(() => tAlias.TaskReminders).WithAlias(() => plannerTask.PersonalTaskReminders),
Projections.Property(() => tAlias.Course).WithAlias(() => plannerTask.Course))
.TransformUsing(Transformers.AliasToBean<PlannerTask>())
.List<PlannerTask>().ToList();
Result: 188 courses with all properties having pretty much the same error
'((new System.Collections.Generic.Mscorlib_CollectionDebugView<Domain.PlannerTask>(result)).Items[0].Course).CoursePermissions' threw an exception of type 'NHibernate.ObjectNotFoundException'
Try 3
Task tAlias = null;
PlannerTask plannerTask = null;
List<PlannerTask> result = session.QueryOver<Task>(() => tAlias)
.Select(Projections.Property(() => tAlias.TaskId).WithAlias(() => plannerTask.TaskId),
Projections.Property(() => tAlias.TaskName).WithAlias(() => plannerTask.TaskName),
Projections.Property(() => tAlias.DueDate).WithAlias(() => plannerTask.DueDate),
Projections.Property(() => tAlias.Description).WithAlias(() => plannerTask.Description),
Projections.ProjectionList().Add(Projections.Property(()=> tAlias.PersonalTaskReminders).WithAlias(() => plannerTask.PersonalTaskReminders)),
Projections.ProjectionList().Add(Projections.Property(()=> tAlias.TaskReminders).WithAlias(() => plannerTask.PersonalTaskReminders)),
Projections.Property(() => tAlias.Course).WithAlias(() => plannerTask.Course))
.TransformUsing(Transformers.AliasToBean<PlannerTask>())
.List<PlannerTask>().ToList();
SELECT this_.TaskId as y0_,
this_.TaskName as y1_,
this_.DueDate as y2_,
this_.Description as y3_,
this_.TaskId as y4_,
this_.TaskId as y4_,
this_.CourseId as y4_
FROM Tasks this_
Result:
CoursePermissions = '((Castle.Proxies.CourseProxy)((new System.Collections.Generic.Mscorlib_CollectionDebugView<PlannerTask>(result)).Items[0].Course)).CoursePermissions' threw an exception of type 'NHibernate.ObjectNotFoundException'
try 4
Try 4
Task tAlias = null;
PlannerTask plannerTask = null;
List<PlannerTask> result = session.QueryOver<Task>(() => tAlias)
.Select(Projections.Property(() => tAlias.TaskId).WithAlias(() => plannerTask.TaskId),
Projections.Property(() => tAlias.TaskName).WithAlias(() => plannerTask.TaskName),
Projections.Property(() => tAlias.DueDate).WithAlias(() => plannerTask.DueDate),
Projections.Property(() => tAlias.Description).WithAlias(() => plannerTask.Description),
Projections.Property(() => tAlias.Course).WithAlias(() => plannerTask.Course))
.TransformUsing(Transformers.AliasToBean<PlannerTask>())
.List<PlannerTask>().ToList();
SELECT this_.TaskId as y0_,
this_.TaskName as y1_,
this_.DueDate as y2_,
this_.Description as y3_,
this_.CourseId as y4_
FROM Tasks this_
Works. I can access everything in the course object.
It seems to have a problem with
tAlias.PersonalTaskReminders and tAlias.TaskReminders. If I remove these Course will render fine.
I don't understand why.
回答1:
I think the problem is you are attempting to project Course proxy objects. Projections are for flat data transfer objects. You can declare the Course properties you need for this view.
public class PlannerTask
{
public int TaskId { get; set; }
public string TaskName { get; set; }
public string Description { get; set; }
public DateTime DueDate { get; set; }
//flatten Course object
public int CourseId { get; set; }
public int CourseName { get; set; }
public bool IsCompleted { get; set; }
}
The select list can be simplified a little...
PlannerTask plannerTask = null;
Course courseAlias = null;
List<PlannerTask> result = session.QueryOver<Task>()
.JoinAlias(x => x.Course, () => courseAlias)
.SelectList(list => list
.Select(x => x.TaskId).WithAlias(() => plannerTask.TaskId)
.Select(x => x.TaskName).WithAlias(() => plannerTask.TaskName)
.Select(x => x.DueDate).WithAlias(() => plannerTask.DueDate)
.Select(x => x.Description).WithAlias(() => plannerTask.Description)
.Select(x => x.Course.Id).WithAlias(() => plannerTask.CourseId))
.Select(x => courseAlias.Name).WithAlias(() => plannerTask.CourseName))
.TransformUsing(Transformers.AliasToBean<PlannerTask>())
.List<PlannerTask>();
来源:https://stackoverflow.com/questions/5923007/how-to-select-with-nhibernate-queryover