[英]Using linq to get part of a list with specific object property
I have: 我有:
List<int> A; //ids list
List<myObject> B;
myObject has 2 properties: myObject具有2个属性:
int id;
string state;
List B includes all the ids of List A and more. 列表B包含列表A的所有ID以及更多。
I would like to get List<myObject> C
which is built of all the ids from List A which are also in state='Idle'. 我想获取
List<myObject> C
,它由来自list A的所有ID组成,它们也处于state ='Idle'。
What is the shortest linq query for this? 最短的linq查询是什么?
you can use LINQ Join + Where
to do it 您可以使用LINQ
Join + Where
做
void Main()
{
List<int> A = new List<int>() {1,2}; //ids list
List<myObject> B = new List<myObject>()
{
new myObject{Id=1,state="Run"},
new myObject{Id=2,state="Idle"},
new myObject{Id=3,state="Idle"},
};
var expectedResult = from t1 in B
join t2 in A on t1.Id equals t2
where t1.state == "Idle"
select t1;
}
// Define other methods and classes here
class myObject
{
public int Id { get; set; }
public string state { get; set; }
}
Here a Step-by-step example with example-data: 以下是包含example-data的分步示例:
class MyObject
{
public int Id { get; set; }
public string State { get; set; }
}
public static void Main(string[] args)
{
List<int> A = new List<int>()
{
1,
2
};
List<MyObject> B = new List<MyObject>()
{
new MyObject() { Id = 1, State = "Idle" },
new MyObject() { Id = 2, State = "Running" },
new MyObject() { Id = 3, State = "Idle" },
};
// Where to filter elements by contidion
var objectsFromA = B.Where(b => A.Contains(b.Id));
Console.WriteLine("Filtered with Id-List 'A': " + string.Join(", ", objectsFromA.Select(s => "\"" + s.Id + ": " + s.State + "\"")));
var onlyIdles = objectsFromA.Where(o => o.State == "Idle");
Console.WriteLine("Filtered only Idle: " + string.Join(", ", onlyIdles.Select(s => "\"" + s.Id + ": " + s.State + "\"")));
// Or in one single Where:
Console.WriteLine("Filtered only Idle: " + string.Join(", ", B.Where(b => A.Contains(b.Id) && b.State == "Idle").Select(s => "\"" + s.Id + ": " + s.State + "\"")));
}
You can use Enumerable.Any
to filter B
by the IDs in A
and in the same query check for the idle state: 您可以使用
Enumerable.Any
通过A
的ID过滤B
,并在同一查询中检查空闲状态:
var idleObjectsQry =
from myObject in B
where A.Any(id => myObject.id = id) && (myObject.state == "Idle")
select myObject;
List<myObject> C = idleObjectsQry.ToList();
You could also use Join
, but in LINQ you generally prefer composition over join, since it is more flexible. 您也可以使用
Join
,但是在LINQ中,您通常更喜欢组合而不是连接,因为它更灵活。
List<myObject> C = B.Where(b => A.Contains(b.Id) && b.state == "Idle").ToList();
尝试像这样使用
List<myObject> C = B.where(x=>x.state =="Idle" && A.contains(x.Id)).select B.ToList();
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