使用 LINQ 汇总任意数据

发布于 2024-10-20 06:10:59 字数 875 浏览 0 评论 0原文

在 C# 中，给定如下所示的类定义：

public class SomeObject
{
    public String A { get; set; }
    public String B { get; set; }
    public String C { get; set; }
}

并给定 SomeObject 的集合，我希望我的应用程序能够计算按 A、B 和 C 的任意组合分组的 SomeObject 的数量。我可以使用 LINQ 查询来执行此操作，或者如果没有，我可以编写一些算法吗？

鉴于此：

List<SomeObject> objects;
bool GroupByA;
bool GroupByB;
bool GroupByC;

如果 GroupByA 为 true，我想按 SomeObject.A 对对象进行分组；如果 GroupByB 为 true，则按 B 对对象进行分组；如果 GroupByC 为 true，则按 C 对对象进行分组。我知道我可以通过 objects.GroupBy(o => oA); 执行其中任何一个，但是接下来我该如何按 B 和/或进行分组C？

我希望这是有道理的。我希望得到的是这样的：

There are 10 objects with A = "Smith" and B = "London"
There are 20 objects with A = "Jones" and B = "London"
There are 44 objects with A = "Jones" and B = "Inverness"

等等等等。提前谢谢你。

原文

In C#, given a class definition like this:

public class SomeObject
{
    public String A { get; set; }
    public String B { get; set; }
    public String C { get; set; }
}

and given a collection of SomeObjects, I want my application to be able to count the number of SomeObjects grouped by any combination of A, B and C. Is there a LINQ query I can use to do this, or if not, some algorithm I can write?

Given this:

List<SomeObject> objects;
bool GroupByA;
bool GroupByB;
bool GroupByC;

I want to group objects by SomeObject.A if GroupByA is true, by B if GroupByB is true, and by C if GroupByC is true. I understand that I can do any one of these by objects.GroupBy(o => o.A); but then how do I then go and group by B and/or C?

I hope that makes sense. What I'm hoping to get out is something like this:

There are 10 objects with A = "Smith" and B = "London"
There are 20 objects with A = "Jones" and B = "London"
There are 44 objects with A = "Jones" and B = "Inverness"

etc. etc. Thank you in advance.

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穿透光 2024-10-27 06:10:59

var groups = objects.GroupBy(o => new {
    A = GroupByA ? o.A : null,
    B = GroupByB ? o.B : null,
    C = GroupByC ? o.C : null
});

foreach (var g in groups)
{
    Console.WriteLine("There are {0} objects with A = {1} and B = {2} and C = {3}",
                 g.Count(),
                 g.Key.A,
                 g.Key.B,
                 g.Key.C);
}

可以进行一些更复杂的格式化来处理 C=null 关键部分。

var groups = objects.GroupBy(o => new {
    A = GroupByA ? o.A : null,
    B = GroupByB ? o.B : null,
    C = GroupByC ? o.C : null
});

foreach (var g in groups)
{
    Console.WriteLine("There are {0} objects with A = {1} and B = {2} and C = {3}",
                 g.Count(),
                 g.Key.A,
                 g.Key.B,
                 g.Key.C);
}

Some more sophisticated formatting can be done to handle C=null key part.

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