[英]Using linq to get part of a list with specific object property
我有:
List<int> A; //ids list
List<myObject> B;
myObject具有2個屬性:
int id;
string state;
列表B包含列表A的所有ID以及更多。
我想獲取List<myObject> C
,它由來自list A的所有ID組成,它們也處於state ='Idle'。
最短的linq查詢是什么?
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; }
}
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 + "\"")));
}
您可以使用Enumerable.Any
通過A
的ID過濾B
,並在同一查詢中檢查空閑狀態:
var idleObjectsQry =
from myObject in B
where A.Any(id => myObject.id = id) && (myObject.state == "Idle")
select myObject;
List<myObject> C = idleObjectsQry.ToList();
您也可以使用Join
,但是在LINQ中,您通常更喜歡組合而不是連接,因為它更靈活。
List<myObject> C = B.Where(b => A.Contains(b.Id) && b.state == "Idle").ToList();
嘗試像這樣使用
List<myObject> C = B.where(x=>x.state =="Idle" && A.contains(x.Id)).select B.ToList();
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