c# - 带有大量嵌套列表的列表上的 LINQ

Question

我在使用嵌套列表时遇到了麻烦。所以我有3个类(class):

public class Class1
{
   public string Name {get;set;}
   public List<Class2> Class2List {get;set;}
}
public class Class2
{
   public string Name {get;set;}
   public List<Class3> Class3List {get;set;}
}
public class Class3
{
   public string Name {get;set;}
}

我想从 Class1 中选择所有 Class3.Name 其中 Class2.Name = "something"并且重要的是结果将是 IEnumerable 字符串 .我该如何解决？

Answer 1

LINQ 表达式可以有多个嵌套 from条款:

// nested from clauses
var names = from c1 in myClass1List
            from c2 in c1.Class2List
            where c2.Name == "something"
            from c3 in c2.Class3List
            select c3.Name;

为了完整起见，这里有两个使用方法语法的变体:

var names = myClass1List
    .SelectMany(c1 => c1.Class2List.Where(c2 => c2.Name == "something"))
    .SelectMany(c2 => c2.Class3List.Select(c3 => c3.Name));

var names = myClass1List
    .SelectMany(c1 => c1.Class2List
        .Where(c2 => c2.Name == "something")
        .SelectMany(c2 => c2.Class3List
            .Select(c3 => c3.Name)));