嵌套列表的LINQ to Entities投影 [英] LINQ to Entities projection of nested list

问题描述

假设这些对象...

class MyClass
{
     int ID {get;set;}
     string Name {get;set;}
     List<MyOtherClass> Things {get;set;}
}

class MyOtherClass
{
     int ID {get;set;}
     string Value {get;set;}
}

如何使用如下所示的投影执行LINQ to Entities Query，这将给我一个列表? IEnumerable可以很好地工作(假设MyClass.Things是IEnumerable，但我需要使用List)

How do I perform a LINQ to Entities Query, using a projection like below, that will give me a List? This works fine with an IEnumerable (assuming MyClass.Things is an IEnumerable, but I need to use List)

MyClass myClass = (from MyClassTable mct in this.Context.MyClassTableSet
                        select new MyClass
                        {
                             ID = mct.ID,
                             Name = mct.Name,
                             Things = (from MyOtherClass moc in mct.Stuff
                                       where moc.IsActive
                                       select new MyOtherClass
                                       {
                                            ID = moc.ID,
                                            Value = moc.Value
                                       }).AsEnumerable()
                        }).FirstOrDefault();

提前感谢您的帮助！

推荐答案

您没有.您必须在L2O中执行此部分.

You don't. You have to do this part in L2O.

所以您可以这样做:

var q = (from MyClassTable mct in this.Context.MyClassTableSet
         select new // note anonymous type; important!
         {
             ID = mct.ID,
             Name = mct.Name,
             Things = (from MyOtherClass moc in mct.Stuff
                       where moc.IsActive
                       select new MyOtherClass
                       {
                           ID = moc.ID,
                           Value = moc.Value
                       }
          }).AsEnumerable();

MyClass myClass = (from mct in q
                   select new MyClass
                   {                 
                       ID = mct.ID,
                       Name = mct.Name,
                       Things = mct.Things.ToList()
                   }).FirstOrDefault();

无法在一个查询中执行此操作.

There's no way to do this in one query.

这篇关于嵌套列表的LINQ to Entities投影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！