[英]LINQ Querying list in list
我有這種情況:
我的模型視圖:
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; }
}
我的查詢:
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()
};
當我打電話時:
subjects.ToList();
我得到例外:
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.
您不能在 linq-to-entities 查詢中調用ToList
。 Linq-to-entities 查詢將始終投射到IEnumerable<T>
所以如果你想要IList<T>
你必須在 linq-to-objects 中調用它。
嘗試這個:
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()
});
您不能也不應該在 IQueryablle 查詢中使用ToList()
。 請注意,此查詢必須翻譯成 SQL。
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