很抱歉写得不好... 我在mvc项目中有以下情形。 我有一个具有列表类型属性的对象，该属性还包含一个列表类型的子级。 如何获取List2子项的cod = 2和List3子项的cod = 9的List1对象。
public class List1
{
public int cod {get;set;}
public List<List2> list2 {get;set;}
}
public class List2
{
public int cod {get; set;}
public List<List3> list3 {get;set;}
}
public class List3
{
public int cod {get;set;}
}
var list1 = new List1() { cod = 1 };
list1.list2 = new List<List2>();
list1.list2.Add(new List2
{
cod = 1,
list3 = new List<List3>(){
new List3{cod = 1},
new List3{cod = 2}
},
});
list1.list2.Add(new List2
{
cod = 2,
list3 = new List<List3>(){
new List3{cod = 7},
new List3{cod = 8},
new List3{cod = 9}
},
});
list1.list2.Add(new List2
{
cod = 2,
list3 = new List<List3>(){
new List3{cod = 7},
new List3{cod = 9},
new List3{cod = 9}
},
});
listFather.Add(list1);
答案 0 :(得分：5)
我认为此版本更容易理解：
// How can I get the List1 object,
// where List2 children have cod = 2,
// and List3 children have cod = 9.
var matches = (from l1 in listFather
from l2 in l1.list2
from l3 in l2.list3
where l2.cod == 2 &&
l3.cod == 9
select l1).Distinct();
每当List1的List2 / List3组合匹配时，您将获得相同的List1实例，因此最后调用Distinct()，以便每个特定实例在结果中仅列出一次。
这是一个完整的例子：
public class List1
{
public int cod { get; set; }
public List<List2> list2 { get; set; }
public override string ToString()
{
StringBuilder sb = new StringBuilder();
sb.AppendLine("l1-cod: " + cod);
foreach(List2 l2 in list2)
{
sb.AppendLine(l2.ToString());
}
return sb.ToString();
}
}
public class List2
{
public int cod { get; set; }
public List<List3> list3 { get; set; }
public override string ToString()
{
StringBuilder sb = new StringBuilder();
sb.AppendLine("\tl2-cod: " + cod);
foreach (List3 l3 in list3)
{
sb.AppendLine("\t\t" + l3.ToString());
}
return sb.ToString();
}
}
public class List3
{
public int cod { get; set; }
public override string ToString()
{
return "l3-cod: " + cod;
}
}
class Program
{
static void Main(string[] args)
{
List<List1> listFather = new List<List1>();
var listA = new List1() { cod = 1 };
listA.list2 = new List<List2>();
listA.list2.Add(new List2
{
cod = 1,
list3 = new List<List3>(){
new List3{cod = 1},
new List3{cod = 2}
},
});
listA.list2.Add(new List2
{
cod = 2,
list3 = new List<List3>(){
new List3{cod = 7},
new List3{cod = 8},
new List3{cod = 9}
},
});
listA.list2.Add(new List2
{
cod = 2,
list3 = new List<List3>(){
new List3{cod = 7},
new List3{cod = 9},
new List3{cod = 9}
},
});
listFather.Add(listA);
var listB = new List1() { cod = 2 };
listB.list2 = new List<List2>();
listB.list2.Add(new List2
{
cod = 1,
list3 = new List<List3>(){
new List3{cod = 1},
new List3{cod = 2}
},
});
listB.list2.Add(new List2
{
cod = 2,
list3 = new List<List3>(){
new List3{cod = 7},
new List3{cod = 8},
new List3{cod = 10}
},
});
listFather.Add(listB);
var listC = new List1() { cod = 5 };
listC.list2 = new List<List2>();
listC.list2.Add(new List2
{
cod = 4,
list3 = new List<List3>(){
new List3{cod = 6},
new List3{cod = 7}
},
});
listC.list2.Add(new List2
{
cod = 2,
list3 = new List<List3>(){
new List3{cod = 7},
new List3{cod = 8},
new List3{cod = 10}
},
});
listFather.Add(listC);
var listD = new List1() { cod = 7 };
listD.list2 = new List<List2>();
listD.list2.Add(new List2
{
cod = 8,
list3 = new List<List3>(){
new List3{cod = 1},
new List3{cod = 2}
},
});
listD.list2.Add(new List2
{
cod = 2,
list3 = new List<List3>(){
new List3{cod = 7},
new List3{cod = 9},
new List3{cod = 1}
},
});
listFather.Add(listD);
Console.WriteLine("All objects:");
foreach(List1 l1 in listFather)
{
Console.WriteLine(l1);
}
Console.WriteLine("----------");
// How can I get the List1 object,
// where List2 children have cod = 2,
// and List3 children have cod = 9.
var matches = (from l1 in listFather
from l2 in l1.list2
from l3 in l2.list3
where l2.cod == 2 &&
l3.cod == 9
select l1).Distinct();
Console.WriteLine("All matches:");
foreach (List1 l1 in matches)
{
Console.WriteLine(l1);
}
Console.WriteLine();
Console.Write("Press Enter to quit");
Console.ReadLine();
}
}
输出：
All objects:
l1-cod: 1
l2-cod: 1
l3-cod: 1
l3-cod: 2
l2-cod: 2
l3-cod: 7
l3-cod: 8
l3-cod: 9
l2-cod: 2
l3-cod: 7
l3-cod: 9
l3-cod: 9
l1-cod: 2
l2-cod: 1
l3-cod: 1
l3-cod: 2
l2-cod: 2
l3-cod: 7
l3-cod: 8
l3-cod: 10
l1-cod: 5
l2-cod: 4
l3-cod: 6
l3-cod: 7
l2-cod: 2
l3-cod: 7
l3-cod: 8
l3-cod: 10
l1-cod: 7
l2-cod: 8
l3-cod: 1
l3-cod: 2
l2-cod: 2
l3-cod: 7
l3-cod: 9
l3-cod: 1
----------
All matches:
l1-cod: 1
l2-cod: 1
l3-cod: 1
l3-cod: 2
l2-cod: 2
l3-cod: 7
l3-cod: 8
l3-cod: 9
l2-cod: 2
l3-cod: 7
l3-cod: 9
l3-cod: 9
l1-cod: 7
l2-cod: 8
l3-cod: 1
l3-cod: 2
l2-cod: 2
l3-cod: 7
l3-cod: 9
l3-cod: 1
Press Enter to quit
答案 1 :(得分：2)
让我尝试一下：
var list = listFather.Select(c => new List1
{
cod = c.cod,
list2 = c.list2.Select(d => new List2
{
cod = d.cod,
list3 = d.list3.Where(x => x.cod == 9).ToList()
}).Where(r => r.cod == 2).ToList()
}).ToList();