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能否舉例c#中g(shù)roup的應(yīng)用場景

c#
小樊
82
2024-09-20 08:02:20
欄目: 編程語言

在C#中，GroupBy是一個非常強(qiáng)大的LINQ（Language Integrated Query）方法，它允許你根據(jù)某個或某些屬性將集合中的元素進(jìn)行分組。以下是一些GroupBy在C#中的常見應(yīng)用場景：

  1. 按類型分組： 假設(shè)你有一個對象列表，每個對象都有一個類型屬性，你可以使用GroupBy來按這個類型屬性對這些對象進(jìn)行分組。

    var people = new List<Person>
{
    new Person { Name = "Alice", Age = 25, Type = "Student" },
    new Person { Name = "Bob", Age = 30, Type = "Employee" },
    new Person { Name = "Charlie", Age = 25, Type = "Student" },
    new Person { Name = "David", Age = 30, Type = "Employee" }
};

var groupedPeople = people.GroupBy(p => p.Type);

foreach (var group in groupedPeople)
{
    Console.WriteLine($"Group: {group.Key}");
    foreach (var person in group)
    {
        Console.WriteLine($"Name: {person.Name}, Age: {person.Age}");
    }
}

  2. 按日期分組： 如果你有一個包含多個日期的對象列表，你可以使用GroupBy來按日期對這些對象進(jìn)行分組。

    var events = new List<Event>
{
    new Event { Date = new DateTime(2023, 1, 1), Name = "New Year's Day" },
    new Event { Date = new DateTime(2023, 1, 10), Name = "Rainy Day" },
    new Event { Date = new DateTime(2023, 2, 14), Name = "Valentine's Day" },
    new Event { Date = new DateTime(2023, 2, 14), Name = "Rainy Day" }
};

var groupedEvents = events.GroupBy(e => e.Date.Date);

foreach (var group in groupedEvents)
{
    Console.WriteLine($"Date: {group.Key}");
    foreach (var @event in group)
    {
        Console.WriteLine($"Name: {@event.Name}");
    }
}

  3. 按地區(qū)分組： 如果你有一個包含多個銷售記錄的對象列表，每個記錄都有一個地區(qū)屬性，你可以使用GroupBy來按地區(qū)對這些記錄進(jìn)行分組，并計算每個地區(qū)的總銷售額。

    var sales = new List<Sale>
{
    new Sale { Region = "North", Amount = 1000 },
    new Sale { Region = "South", Amount = 1500 },
    new Sale { Region = "East", Amount = 750 },
    new Sale { Region = "West", Amount = 1250 },
    new Sale { Region = "South", Amount = 500 }
};

var groupedSales = sales.GroupBy(s => s.Region).ToDictionary(g => g.Key, g => g.Sum(s => s.Amount));

foreach (var region in groupedSales.Keys)
{
    Console.WriteLine($"Region: {region}, Total Sales: {groupedSales[region]}");
}

  4. 按字符串的首字母分組： 你可以按字符串的首字母對字符串?dāng)?shù)組進(jìn)行分組，這在創(chuàng)建字典或進(jìn)行其他需要分組的操作時非常有用。

    var words = new string[] { "Apple", "Banana", "Cherry", "Date", "Elderberry" };

var groupedWords = words.GroupBy(w => w[0]);

foreach (var group in groupedWords)
{
    Console.WriteLine($"First Letter: {group.Key}");
    foreach (var word in group)
    {
        Console.WriteLine(word);
    }
}

這些示例展示了GroupBy在C#中的多樣性和實用性。你可以根據(jù)你的具體需求調(diào)整分組依據(jù)和后續(xù)操作。

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