C# 如何使用 Linq 在 List 中找到对象？
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How can I find object in List with Linq?
提问by Alexandr
I have a object:
我有一个对象：
public class MyObject
{
public int Id { get; set; }
public List<MyObject> Items { get; set; }
}
And I have list of MyObject:
我有 MyObject 列表：
List<MyObject> collection = new List<MyObject>();
collection.Add(new MyObject()
{
Id = 1,
Items = null
});
collection.Add(new MyObject()
{
Id = 2,
Items = null
});
collection.Add(new MyObject()
{
Id = 3,
Items = null
});
List<MyObject> collectionMyObject = new List<MyObject>();
collectionMyObject.Add(new MyObject()
{
Id = 4,
Items = collection
});
collectionMyObject.Add(new MyObject()
{
Id = 5,
Items = null
});
How can I find object with Id = 2 in collectionMyObject with Linq ?
如何使用 Linq 在 collectionMyObject 中找到 Id = 2 的对象？
采纳答案by Andrei
If you are trying to find an object in collectionMyObjectwhich has item with id 2, then this should work:
如果您正在尝试查找collectionMyObject包含 id 为 2 的项目的对象，那么这应该可以工作：
MyObject myObject = collectionMyObject.FirstOrDefault(o => o.Items != null && o.Items.Any(io => io.Id == 2));
And if you are try to find an inner item with id 2, then this query with SelectManymight be helpful:
如果您尝试查找 id 为 2 的内部项目，那么此查询SelectMany可能会有所帮助：
MyObject myObject1 = collectionMyObject.Where(o => o.Items != null).SelectMany(o => o.Items).FirstOrDefault(io => io.Id == 2);
回答by Belogix
Using the Wherekeyword and a lambda like so:
Where像这样使用关键字和 lambda：
MyObject result = collectionMyObject.Where(x => x.Id == 2).FirstOrDefault()
Or, to find in the Itemssub-collection simply do:
或者，要在Items子集合中查找，只需执行以下操作：
MyObject result = collectionMyObject.Where(x => x.Item.Id == 2).FirstOrDefault()
回答by DGibbs
Simple:
简单的：
var obj = collectionMyObject.FirstOrDefault(o => o.Id == 2);
回答by orel
var item = collectionMyObject.FirstOrDefault(x => x.Id == 2);
EDIT: I misread the question so Andrei's answer looks better than mine.
编辑：我误读了这个问题，所以安德烈的回答看起来比我的好。
回答by Sandy
Another way may be:
另一种方式可能是：
(from c in collection where c.Id == 2 select c).ToList;
(from c in collection where c.Id == 2 select c).ToList;
It should give a list in return. If want a single entry, then replace ToList()with FirstOrDefault().
它应该给出一个列表作为回报。如果想要单个条目，则替换ToList()为FirstOrDefault().
Hope it helps.
希望能帮助到你。
