LINQ查询列表中的列表 [英] LINQ Querying list in list
本文介绍了LINQ查询列表中的列表的处理方法,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
我有这种情况:
我的ModelView:
My ModelView:
public class Subject
{
public int ID { get; set; }
public string Name { get; set; }
public int ProfessorID { get; set; }
public string ProfessorFullName{ get; set; }
public IList<Assistant> Assistants { get; set; }
}
public class Assistant
{
public string AssistantFullName{ get; set; }
}
我的查询:
var subjects = from subject in Entities.Subjects
from professor in subject.Lecturers
where professor.Professor == true
select new SSVN.ModelView.Subject()
{
ID = subject.ID,
Name= subject.Name,
ProfessorFullName= professor.LastName+ " " + professor.Name,
Assistants= (from subject1 in Entities.Subjects
from assistant in subject1.Lecturers
where assistant.Professor == false
select new SSVN.ModelView.Assistant()
{
AssistantFullName = assistant.LastName+ " " + assistant.Name
}).ToList()
};
当我打电话时:
subjects.ToList();
我遇到异常:
LINQ to Entities does not recognize the method
'System.Collections.Generic.List`1[SSVN.ModelView.Assistant] ToList[Assistant]
(System.Collections.Generic.IEnumerable`1[SSVN.ModelView.Assistant])' method, and this
method cannot be translated into a store expression.
推荐答案
您不能在linq-to-entities查询中调用ToList
. Linq-to-entities查询将始终投射到IEnumerable<T>
,因此如果要IList<T>
,则必须在linq-to-objects中调用它.
You cannot call ToList
inside linq-to-entities query. Linq-to-entities query will always project to IEnumerable<T>
so if you want IList<T>
you must call it in linq-to-objects.
尝试一下:
var subjects = (from subject in Entities.Subjects
from professor in subject.Lecturers
where professor.Professor == true
select new
{
ID = subject.ID,
Name= subject.Name,
ProfessorFullName= professor.LastName+ " " + professor.Name,
Assistants= (from subject1 in Entities.Subjects
from assistant in subject1.Lecturers
where assistant.Professor == false
select new SSVN.ModelView.Assistant()
{
AssistantFullName = assistant.LastName+ " " + assistant.Name
})
}).AsEnumerable().Select(x => new SSVN.ModelView.Subject
{
ID = x.ID,
Name = x.Name,
ProfessorFullName = X.ProffesorFullName,
Assistants = x.Assistants.ToList()
});
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