C# 按特定元素按列表分组以生成列表列表

Question

我有一个list 的对象。每个对象都有这些组件：index, countNr, descA, descB.

我如何按（可能是 LINQ）这个 list 和 countNr 值分组？

喜欢：

列表 = {(1,3,a1,b1), (2,2,a2,b2), (3,2,a3,b3), (4,1,a4,b4), (5,1,a5,b5), (6,1,a6,b6), (7,1,a7,b7)}

我现在想要另一个newList 列表，其中该列表中的位置表示countNr 编号，例如：

newList = {{(7,1,a7,b7), (6,1,a6,b6), (5,1,a5,b5), (4,1,a4,b4)},  {(3,2,a3,b3), (2,2,a2,b2)},  {(1,3,a1,b1)}}

Answer 1

如果你的班级是这样的：

public class MyClass
{

    public MyClass(int index, int countNr, string descA, string descB)
    {
        Index = index;
        CountNr = countNr;
        DescA = descA;
        DescB = descB;
    }
    public int Index { get; set; }
    public int CountNr { get; set; }
    public string DescA { get; set; }
    public string DescB { get; set; }
}

这个输入：

var list = new List<MyClass> {
    new MyClass(1, 3, "a1", "b1"),
    new MyClass(2, 2, "a2", "b2"),
    new MyClass (3, 2, "a3", "b3"),
    new MyClass(4, 1, "a4", "b4"),
    new MyClass(5, 1, "a5", "b5"),
    new MyClass(6, 1, "a6", "b6"),
    new MyClass(7, 1, "a7", "b7") };

你可以试试：

var query = from r in list
    group r by new { r.CountNr } into grp
    orderby grp.Key.CountNr ascending
    select new
    {
        grp.Key.CountNr,
        grp
    };

那么你有这个：

foreach (var item in query)
{
    System.Diagnostics.Debug.WriteLine($"CountNr: {item.CountNr}"); //Key  or group
    //All rows of group
    foreach (var g in item.grp)
    {
        System.Diagnostics.Debug.WriteLine($"{g.Index} - {g.CountNr} - {g.DescA} - {g.DescB}");
    }                
}

这个结果：

CountNr: 1
4 - 1 - a4 - b4
5 - 1 - a5 - b5
6 - 1 - a6 - b6
7 - 1 - a7 - b7
CountNr: 2
2 - 2 - a2 - b2
3 - 2 - a3 - b3
CountNr: 3
1 - 3 - a1 - b1

如果您也需要按索引订购。试试这个：

var query = from r in list
    group r by new { r.CountNr } into grp
    orderby grp.Key.CountNr ascending
    select new
    {
        grp.Key.CountNr,
        grp =grp.OrderByDescending( c=> c.Index)
    };

你有这个结果：

CountNr: 1
7 - 1 - a7 - b7
6 - 1 - a6 - b6
5 - 1 - a5 - b5
4 - 1 - a4 - b4
CountNr: 2
3 - 2 - a3 - b3
2 - 2 - a2 - b2
CountNr: 3
1 - 3 - a1 - b1

委托人

Answer 2

newList = list.OrderBy(z => z.countNr).ThenByDescending(y => y.index).ToList()

可能是你想要的。我认为它可能会根据您的示例输入生成您的示例输出。

或完整的代码示例：

class Bob
{
    public int index;
    public int countNr;
    public string descA;
    public string descB;

    public Bob(int index, int countNr, string descA, string descB)
    {
        this.index = index;
        this.countNr = countNr;
        this.descA = descA;
        this.descB = descB;
    }

    public override string ToString()
    {
        return $"{index} - {countNr} - {descA} - {descB}";
    }
}

class Program
{
    static void Main(string[] args)
    {
        var list = new List<Bob>
        {
            new Bob(1, 3, "a1", "b1"),
            new Bob(2, 2, "a2", "b2"),
            new Bob(3, 2, "a3", "b3"),
            new Bob(4, 1, "a4", "b4"),
            new Bob(5, 1, "a5", "b5"),
            new Bob(6, 1, "a6", "b6"),
            new Bob(7, 1, "a7", "b7")
        };

        var newList = list.OrderBy(z => z.countNr).ThenByDescending(y => y.index).ToList();

        newList.ForEach(Console.WriteLine);

        Console.ReadLine();
    }
}

给出：

7 - 1 - a7 - b7
6 - 1 - a6 - b6
5 - 1 - a5 - b5
4 - 1 - a4 - b4
3 - 2 - a3 - b3
2 - 2 - a2 - b2
1 - 3 - a1 - b1