如何“选择"使用 nhibernate 查询 [英] How to "Select" with nhibernate queryover
本文介绍了如何“选择"使用 nhibernate 查询的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！
问题描述
我想通过查询返回一个对象
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; }
}
尝试 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();
结果:188 条记录，课程对象全为空.
result: 188 records with all null for course object.
尝试 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();
结果:188 门课程，所有属性都有几乎相同的错误
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'
尝试 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_
结果:
CoursePermissions = '((Castle.Proxies.CourseProxy)((new System.Collections.Generic.Mscorlib_CollectionDebugView<PlannerTask>(result)).Items[0].Course)).CoursePermissions' threw an exception of type 'NHibernate.ObjectNotFoundException'
尝试 4
尝试 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_
作品.我可以访问课程对象中的所有内容.
Works. I can access everything in the course object.
好像有问题
tAlias.PersonalTaskReminders 和 tAlias.TaskReminders.如果我删除这些课程会很好.
tAlias.PersonalTaskReminders and tAlias.TaskReminders. If I remove these Course will render fine.
我不明白为什么.
推荐答案
我认为问题在于您正在尝试投影课程代理对象.投影用于平面数据传输对象.您可以声明此视图所需的课程属性.
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; }
}
选择列表可以简化一点...
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>();
这篇关于如何“选择"使用 nhibernate 查询的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
查看全文
