Question

我有一个项目列表，每个项目都包含一个组件列表。

public class Item
{
    Item(string name)
    {
        ItemName = name;
    }
    public string ItemName { get; private set; }
    public List<Component> Components {get;set;}
}

public class Component
{
    public string Name {get;set;}
    public string Status {get;set;}
}

// Example
Item 1
    Component 1 - Status A
    Component 2 - Status B
    Component 3 - Status A
Item 2
    Component 1 - Status C
    Component 2 - Status C
    Component 3 - Status A
Item 3
    Component 1 - Status C
    Component 2 - Status C
    Component 3 - Status D

使用LINQ，我如何只获得其状态为A或B的组件的所有项目的组件？

以下解决方案不是我想要的：

var statuses = { "A" , "B" }
var result= items
                .Where(i => i.Components
                .Any(c => statuses.Contains(c.Status))
                .ToList();

此解决方案返回包含所有组件的项目，以防至少一个组件具有状态A或B.在我们的示例中，将返回项目1和2及其所有组件。结果将是：

Item 1
    Component 1 - Status A
    Component 2 - Status B
    Component 3 - Status A
Item 2
    Component 1 - Status C
    Component 2 - Status C
    Component 3 - Status A

我需要一个类似的解决方案，其结果将是：

Item 1
    Component 1 - Status A
    Component 2 - Status B
    Component 3 - Status A
Item 2
    Component 3 - Status A

仅返回状态为A和B的组件。

实现此任务的正确语法是什么？

修改

按要求，初始化项目：

var items = new List<Item>
{
    new Item("Item 1")
    {
        Components = new List<Component>
        {
            new Component {Name ="Component1", Status = "A"},
            new Component {Name ="Component2", Status = "B"},
            new Component {Name ="Component3", Status = "A"}
         }
     },
     new Item("Item 2")
     {
         Components = new List<Component>
         {
            new Component {Name ="Component1", Status = "C"},
            new Component {Name ="Component2", Status = "C"},
            new Component {Name ="Component3", Status = "A"}
         }
     },
     new Item("Item 3")
     {
         Components = new List<Component>
         {
             new Component {Name ="Component1", Status = "C"},
             new Component {Name ="Component2", Status = "C"},
             new Component {Name ="Component3", Status = "D"}
          }
     }
};

Answer 1

探索可能的途径：

var statuses = new HashSet<string>() { "A", "B" };
var result = items
    .Where(i => i.Components.Any(c => statuses.Contains(c.Status)))
    .Select(z => new Item(z.ItemName) { Components = z.Components.Where(y => statuses.Contains(y.Status)).ToList() })
    .ToList();

为此，您需要将Item构造函数设为公共。

Answer 2

我只是为了完整而包含这个（因为我没有足够的声誉来评论）。如果你只想要没有包含项目的组件，你可以这样做。

string[] statuses = { "A", "B" };
var things = items.SelectMany(x => x.Components.Where(y => statuses.Contains(y.Status)));

foreach (var thing in things)
    Console.WriteLine(thing);

如何使用LINQ

2 个答案: