Question

考虑到下面的情况，我需要获得属于分配给顶层的中间对象列表的所有底层级对象。我所拥有的结构意味着中层对象悬挂在顶层，但底层只是所有的集合。因此，即使列表不存在，我也需要获得有效“挂掉”顶层和中层的所有底层对象。在lambda中有一个很好的方法吗？

class Program
{
    static void Main(string[] args)
    {
        List<TopClass> topClasses = new List<TopClass>();

        List<MiddleClass> mcList1 = new List<MiddleClass>();
        mcList1.Add(new MiddleClass(1));
        mcList1.Add(new MiddleClass(3));
        mcList1.Add(new MiddleClass(5));
        TopClass tc1 = new TopClass(1, mcList1);
        topClasses.Add(tc1);

        List<MiddleClass> mcList2 = new List<MiddleClass>();
        mcList2.Add(new MiddleClass(2));
        mcList2.Add(new MiddleClass(4));
        TopClass tc2 = new TopClass(2, mcList2);
        topClasses.Add(tc2);

        List<MiddleClass> mcList3 = new List<MiddleClass>();
        mcList3.Add(new MiddleClass(6));
        mcList3.Add(new MiddleClass(7));
        TopClass tc3 = new TopClass(3, mcList3);
        // ** Note not added to the global list

        List<BottomClass> bottomClasses = new List<BottomClass>();
        bottomClasses.Add(new BottomClass(10, 1));
        bottomClasses.Add(new BottomClass(20, 2));
        bottomClasses.Add(new BottomClass(30, 3));
        bottomClasses.Add(new BottomClass(40, 4));
        bottomClasses.Add(new BottomClass(50, 5));
        bottomClasses.Add(new BottomClass(60, 6));
        bottomClasses.Add(new BottomClass(70, 7));

        bottomClass.FindAll(b => ....?
    }
}

public class TopClass //Instruments
{
    public int Id { get; set; }
    public List<MiddleClass> MiddleClasses { get; set; }

    public TopClass(int id, List<MiddleClass> middleClasses)
    {
        this.Id = id;
        this.MiddleClasses = middleClasses;
    }
}

public class MiddleClass // Sequences
{
    public int Id { get; set; }

    public MiddleClass(int id)
    {
        this.Id = id;
    }
}


public class BottomClass //SequenceItem
{
    public int Id { get; set; }
    public int MiddleClassId { get; set; }

    public BottomClass(int id, int middleClassId)
    {
        this.Id = id;
        this.MiddleClassId = middleClassId;
    }
}

结果将是一个包含10到50但不包含60和70的列表。

Answer 1

怎么样

topClasses
 .SelectMany(x=>x.MiddleClasses)
 .SelectMany(x=>bottomClasses.Where(y=>y.MiddleClassId==x.Id))

可选择在末尾添加.Distinct()以获得唯一性

或者从另一方面

bottomClasses.Where(
  b=>topClasses.Any(t=>t.MiddleClasses.Any(m=>m.Id==b.MiddleClassId))
)

Answer 2

不确定这是不是你想要的......

var test = bottomClasses.Where(b => b.Id >= 10 && b.Id <= 50);

如果没有，请评论我错误解释的内容：）

Answer 3

这就是你想要的。所以给出一个TopClass，例如tc3，这将为你提供tc3

之外的所有底层课程

   var allMiddleClasses = topClasses.SelectMany(t => t.MiddleClasses);

    var allBC = 
            bottomClasses
                .Where(b => allMiddleClasses.Select(m => m.Id).Contains(b.MiddleClassId))
                    .ToList();

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3 个答案: