C# System.Linq.Dynamic.Core：如何正确选择多个？

我是这个系统的新手。Linq.Dynamic.Core。我有这个：

var equipments= from pack in Packs where pack.Equipments.Any() select pack.Equipments;

var secondEquipments = from pac in equipments where       
pac.GenericEquipment.Id == 2 select pac;
//I could use one variable instead of 2 but that would look a little bit complex

假设我们有：

Packs = new List<Pack>
{
    new Pack()
    {
        IdAtSource="Pack1",
        Equipments= new List<Equipment>()
        {
            new Equipment
            {
                Id=1,
                GenericEquipment = new GenericEquipment()
                {
                    Id=7
                }
            }
        }
    },
    new Pack()
    {
        IdAtSource="Pack2",
        Equipments= new List<Equipment>()
        {
            new Equipment
            {
                Id=2,
                GenericEquipment = new GenericEquipment()
                {
                    Id=1
                }
            },
            new Equipment
            {
                Id=2,
                GenericEquipment = new GenericEquipment()
                {
                    Id=2
                }
            }
        }
    }
}

var equipments= from pack in Packs where pack.Equipments.Any() select pack.Equipments;

var secondEquipments = from pac in equipments where       
pac.GenericEquipment.Id == 2 select pac;
//I could use one variable instead of 2 but that would look a little bit complex

但我觉得我是这里的靶子。还有关于如何使用这个库的文档页吗

var equipments= from pack in Packs where pack.Equipments.Any() select pack.Equipments;

var secondEquipments = from pac in equipments where       
pac.GenericEquipment.Id == 2 select pac;
//I could use one variable instead of 2 but that would look a little bit complex

---

非常感谢

这些应该有用：

var equipments= from pack in Packs where pack.Equipments.Any() select pack.Equipments;

var secondEquipments = from pac in equipments where       
pac.GenericEquipment.Id == 2 select pac;
//I could use one variable instead of 2 but that would look a little bit complex

Msdn链接（很抱歉，我在手机上，无法重命名）：

---

动态LINQ的最新版本似乎是该项目及其文档

var equipments= from pack in Packs where pack.Equipments.Any() select pack.Equipments;

var secondEquipments = from pac in equipments where       
pac.GenericEquipment.Id == 2 select pac;
//I could use one variable instead of 2 but that would look a little bit complex

---

通常，您需要动态LINQ而不是标准LINQ的唯一原因是当编译时类型未知时

var equipments= from pack in Packs where pack.Equipments.Any() select pack.Equipments;

var secondEquipments = from pac in equipments where       
pac.GenericEquipment.Id == 2 select pac;
//I could use one variable instead of 2 but that would look a little bit complex

如果您在编译时知道查询将针对

列表

，则可以使用stanadard LINQ，如下代码所示（请注意，这将修改

包

的原始实例）：

var equipments= from pack in Packs where pack.Equipments.Any() select pack.Equipments;

var secondEquipments = from pac in equipments where       
pac.GenericEquipment.Id == 2 select pac;
//I could use one variable instead of 2 but that would look a little bit complex

如果需要不修改原始实例的代码，此代码将创建原始实例的副本：

var equipments= from pack in Packs where pack.Equipments.Any() select pack.Equipments;

var secondEquipments = from pac in equipments where       
pac.GenericEquipment.Id == 2 select pac;
//I could use one variable instead of 2 but that would look a little bit complex

var usefulPacks = Packs.Select(pack => {
    return new Pack() {
        IDAtSource = pack.IDAtSource,
        Equipments = pack.Equipments.Where(equipment => 
            equipment.GenericEquipment.Id == 1
        ).ToList(); 
    };
}).Where(pack => pack.Equipments.Any()).ToList();

请注意，这不是使用

。SelectMany

-

。SelectMany

用于从嵌套的枚举创建单个枚举；这里，最终列表中的每个

Pack

对应于原始列表中的一个

Pack

var equipments= from pack in Packs where pack.Equipments.Any() select pack.Equipments;

var secondEquipments = from pac in equipments where       
pac.GenericEquipment.Id == 2 select pac;
//I could use one variable instead of 2 but that would look a little bit complex

---

动态LINQ不支持在表达式中修改或初始化属性：

var equipments= from pack in Packs where pack.Equipments.Any() select pack.Equipments;

var secondEquipments = from pac in equipments where       
pac.GenericEquipment.Id == 2 select pac;
//I could use one variable instead of 2 but that would look a little bit complex

表达式语言允许获取（但不设置）任何可访问的公共字段、属性或索引器的值

var equipments= from pack in Packs where pack.Equipments.Any() select pack.Equipments;

var secondEquipments = from pac in equipments where       
pac.GenericEquipment.Id == 2 select pac;
//I could use one variable instead of 2 but that would look a little bit complex

因此，

设备

属性不能更改/初始化为仅包含符合条件的

设备

实例

var equipments= from pack in Packs where pack.Equipments.Any() select pack.Equipments;

var secondEquipments = from pac in equipments where       
pac.GenericEquipment.Id == 2 select pac;
//I could use one variable instead of 2 but that would look a little bit complex

要设置

设备

，您有两种选择：

var equipments= from pack in Packs where pack.Equipments.Any() select pack.Equipments;

var secondEquipments = from pac in equipments where       
pac.GenericEquipment.Id == 2 select pac;
//I could use one variable instead of 2 but that would look a little bit complex

将构造函数添加到

Pack

，该构造函数采用适当的参数

在任何具有适当参数的类上编写静态方法

---

将构造函数添加到

Pack

var equipments= from pack in Packs where pack.Equipments.Any() select pack.Equipments;

var secondEquipments = from pac in equipments where       
pac.GenericEquipment.Id == 2 select pac;
//I could use one variable instead of 2 but that would look a little bit complex

您可以使用适当的参数将构造函数添加到

Pack

，以设置

设备

：

var equipments= from pack in Packs where pack.Equipments.Any() select pack.Equipments;

var secondEquipments = from pac in equipments where       
pac.GenericEquipment.Id == 2 select pac;
//I could use one variable instead of 2 but that would look a little bit complex

Pack(int IDAtSource, IEnumerable<Equipment> equipments) {
    this.IDAtSource = IDAtSource;
    this.Equipments = equipments.ToList();
}

---

定义静态方法

var equipments= from pack in Packs where pack.Equipments.Any() select pack.Equipments;

var secondEquipments = from pac in equipments where       
pac.GenericEquipment.Id == 2 select pac;
//I could use one variable instead of 2 but that would look a little bit complex

public static class MyPackMethods {
    public static Pack Create(int IDAtSource, IEnumerable<Equipment> equipments) {
        return new Pack() {
            IDAtSource = IDAtSource,
            Equipments = equipments.ToList()
        };
    }
}

---

谢谢你，好心的先生！但是这并没有回答我的问题，关于如何使用库Linq.Dynamic.Core。没问题，但我认为这回答了你的问题。请让我更正一下：）非常感谢你的回答！事实上，它几乎回答了我的问题。当我完成选择时，我需要有一个包，只有那些具有Id=1的通用设备的设备。在设备清单中，只有一台设备应显示。而且，我不知道运行时的类型，这只是一个简单的例子。再次感谢，您的asnwer非常有帮助。@这就是动态LINQ查询中发生的事情。首先，我们调用

。选择
，这将为
Pack
的每个初始实例创建一个
Pack
的新实例，但只将匹配的
设备
传递给新实例的构造函数：
设备。其中（GenericEquipment.ID=1）
；然后我们调用
.Where
，只包括
包
的实例，这些实例在
设备
属性中有一些内容。明白了，亲爱的先生。但不幸的是，这不是一个改变构造函数的选项，所以我可以使用这个解决方案。