C#代码描述需要帮助 [英] c# code description need help

问题描述

我有这段代码，但实际上我并不理解这里发生的事情，任何人都可以向我解释一下代码:

hi I have this code but in fact I dont understant what happen here can any one explain me the code :

ordering.GroupBy(name=> name).OrderByDescending(g => g.Count())

我不理解(name=>name)和(g=>g.count)仅在这部分中对我有帮助

I dont understand (name=>name) and (g=>g.count) help me only in this part

推荐答案

您可能会通过以下内容更好地理解这一点

name => name 与f(name) = name相同，只是您不需要包括函数名称(在这种情况下，函数名称为f)

因此，第一个ordering.GroupBy(name => name)表示您希望分组符合名称.现在，此代码创建了一个键，在这种情况下，键仅具有name 以及具有相同name的记录(对象)的集合.
在第二部分中发生的是，您正在对每个记录下的记录进行计数，这些记录是具有相同键或在这种情况下具有相同字符串的原始记录的集合.作为功​​能，这将是f(keyCollection) = keyCollection.Count().

这可能会有所帮助:

定义一个类:

You might understand this better by the following

name => name is the same as f(name) = name, just that you do not need to include a function name (in this care the function name is f)

Therefore the first ordering.GroupBy(name => name) is saying that you want the grouping to be according the the name. Now this code creates a key that in this case only has the name and a collection of records (objects) that have the same name.

What is happening in the second part is that you are counting the records under each record which is a collection of original records that have the same key, or in this case are the same string. As a function this would be f(keyCollection) = keyCollection.Count().

This might help:

Define a class:

public class t
{
    public string Shortname { get; set; }
    public string Longname { get; set; }
}

然后将其放在控制台程序中:

Then put this in a console program:

var testclass = new t[] {new t {Shortname = "US", Longname = "Long US 1"},
    new t {Shortname = "US", Longname = "Long US 2"},
    new t {Shortname = "UK", Longname = "Long UK 1"},};

var testLinq = testclass.GroupBy(i => i.Shortname);

foreach (var g in testLinq)
{
    Console.WriteLine("Key = " + g.Key);
    Console.WriteLine("  Records");
    foreach (var r in g)
        Console.WriteLine("   " + r.Longname);
    Console.WriteLine();
}

Console.ReadLine();

您将获得以下内容:

You will get the following:

Key = US
  Records
   Long US 1
   Long US 2

Key = UK
  Records
   Long UK 1

这很好文章它如何在C#? -第3部分(详细介绍了C#LINQ) [

This is a nice article How does it work in C#? - Part 3 (C# LINQ in detail)[^]

Please read it and it will help you.

Thanks

那些是lambdas，

Those are lambdas,

name => name

将name作为参数并返回name

Takes name as an argument and returns name

g => g.count

将g作为参数并返回g.Count()

因此，它按名称将它们分组，然后按每个组中的项目数对其进行排序.

Takes g as an argument and returns g.Count()

So it groups them by name, then orders them by the number of items in each group.

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