c# linq GroupBy 对 List 中的 List 的值

Question

我有一个对象列表，在对象中有一个字符串列表。我想要做的是找出每个字符串值有多少。

因此，要使用团队中的人员使用的语言创建一个简单的示例。

public class PeopleLanguages
{
    public string Name;
    public List<string> Languages;
}

创建测试数据...

List<PeopleLanguages> peopleLanguages = new List<PeopleLanguages>();

peopleLanguages.Add(new PeopleLanguages { Name = "Rod", Languages = new List<string> { "English", "French", "German" } });
peopleLanguages.Add(new PeopleLanguages { Name = "Jane", Languages = new List<string> { "English", "Spanish", "Greek" } });
peopleLanguages.Add(new PeopleLanguages { Name = "Fredie", Languages = new List<string> { "French", "Arabic", "Italian" } });
peopleLanguages.Add(new PeopleLanguages { Name = "Viktor", Languages = new List<string> { "English", "Krakozhian" } });

可视化数据：

 * Rod => English | French | German
 * Jane => English | Spanish | Greek
 * Fredie => French | Arabic | Italian
 * Viktor => English | Krakozhian

我可以通过使用 SelectMany().Distinct() 查找不同的字符串值然后在 foreach 循环中匹配来获得我想要的结果：

foreach (string language in peopleLanguages.SelectMany(p => p.Languages).Distinct())
{
    Console.WriteLine($"{language} = {peopleLanguages.Where(p => p.Languages.Contains(language)).Count()}");
}

输出：

English = 3
French = 2
German = 1
Spanish = 1
Greek = 1
Arabic = 1
Italian = 1
Krakozhian = 1

但必须有更好的方法来使用GroupBy()。

我只是不知道如何从语言列表中获取各个不同的值。

Answer 1

Demo on dotnet fiddle

您可以使用SelectMany 获取列表语言列表，然后使用GroupBy 如下所示

var result = peopleLanguages
    .SelectMany(p => p.Languages)
    .GroupBy(p => p);
    
foreach(var item in result)
{
    Console.WriteLine($"{item.Key} : {item.Count()}");
}

输出

English : 3
French : 2
German : 1
Spanish : 1
Greek : 1
Arabic : 1
Italian : 1
Krakozhian : 1