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Accepted
Anton Charov
Asked:2020-12-18 02:23:41 +0000 UTC2020-12-18 02:23:41 +0000 UTC

LINQ groupby 分组排序

  • 772

需要按有效期对所有托盘进行分组，按有效期升序排序，在每组中按重量对托盘进行分类。

class Pallete
{
    public List<Box> boxes { get; private set; }
    public DateTime? getExpirationDate() {
        return boxes.Min(b => b.ExpirationDate);
    }

    public int getWeight() {
        return boxes.Sum(b => b.Weight) + 30;
    }
}

结果是按到期日期对所有托盘进行分组，按到期日期升序排序。现在如何在每组中按重量排序？

private List<Pallete> palletes;

    public void getGroupedBy() {
        var g = palletes
            .GroupBy(p => p.getExpirationDate())
            .OrderBy(p => p.Key);

        foreach (var x in g)
        {
            System.Console.WriteLine("ExDate:{0}", x.Key);
            foreach (var y in x)
            {
                System.Console.WriteLine("=====weight:{0}, id:{1}", y.getWeight(), y.Id);
            }
        }
    }

更新 这样做了

    public void getGroupedBy() {
        var g = palletes
            .GroupBy(p => p.getExpirationDate())
            .OrderBy(p => p.Key)
            .ToDictionary(p => p.Key, p => p.OrderBy(p => p.getWeight()))
            .GroupBy(p => p.Key);

        foreach (var x in g)
        {
            System.Console.WriteLine("ExDate:{0}", x.Key);
            foreach (var y in x)
            {
                System.Console.WriteLine("==ExDate:{0}", y.Key);
                foreach (var z in y.Value) {
                    System.Console.WriteLine("=====weight:{0}, id:{1}", z.getWeight(), z.Id);
                }
            }
        }
    }

在我看来是歪的。是否有可能以某种方式改进最终的结构？导致IGrouping？

c#

1 个回答

  1. Best Answer

    您也在进行后期排序ToDictionary，GroupBy这可能会弄乱元素的顺序。排序操作必须是最后一个才能保证这种排序。例子

    var g = palletes
    .GroupBy(p => p.getExpirationDate())
    .Select(x => new { x.Key, Items = x.OrderBy(z=>z.getExpirationDate()).ToArray() })
    .OrderBy(p => p.Key).ToArray();

foreach (var x in g)
{
    System.Console.WriteLine("ExDate:{0}", x.Key);
    foreach (var y in x.Items)
    {
        System.Console.WriteLine("=====weight:{0}, id:{1}", y.getWeight(), y.Id);
    }
}

    如果您需要将其包装在一个函数中

    public Tuple<DateTime?, Pallete[]>[] Foo()
{
    var g = palletes
    .GroupBy(p => p.getExpirationDate())
    .Select(x => Tuple.Create(x.Key, x.OrderBy(z => z.getExpirationDate()).ToArray()))
    .OrderBy(p => p.Item1).ToArray();

    foreach (var x in g)
    {
        System.Console.WriteLine("ExDate:{0}", x.Item1);
        foreach (var y in x.Item2)
        {
            System.Console.WriteLine("=====weight:{0}, id:{1}", y.getWeight(), y.Id);
        }
    }       
    return g;
}
    • 1

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