前言
在最新的 .NET 9 Alpha 版本中,LINQ(语言集成查询)引入了新方法,增强了数据操作的简单性和可读性。这些方法为常见任务提供了一种更直观的方法,例如根据特定键对元素进行计数和聚合,从而降低了复杂性
.NET9 Before
.NET9之前操作如下代码,较多。
using System;
using System.Collections.Generic;
using System.Linq;
class Program
{
static void Main()
{
// Define a list of users
var users = new List<User>
{
new User { Name = "Alice", Role = "Admin" },
new User { Name = "Bob", Role = "Member" },
new User { Name = "Charlie", Role = "Admin" },
new User { Name = "David", Role = "Member" },
new User { Name = "Eve", Role = "Guest" },
new User { Name = "Frank", Role = "Admin" }
};
// CountBy Role using GroupBy and Select
var roleCounts = users
.GroupBy(user => user.Role) // Group users by their roles
.Select(group => new { Role = group.Key, Count = group.Count() }); // Select the role and count for each group
// Print the results
foreach (var roleCount in roleCounts)
{
Console.WriteLine($"Role: {roleCount.Role}, Count: {roleCount.Count}");
}
}
}
// User class definition
public class User
{
public string Name { get; set; }
public string Role { get; set; }
// Add more properties if needed
}
.NET9 after
随着 .NET 9 的引入,可以使用更简洁、更直观的代码实现相同的操作。通过在内部处理分组和计数来简化过程,直接返回一个集合,其中键是组,值是该组中元素的计数
foreach (var roleCount in users.CountBy(user => user.Role))
{
Console.WriteLine($"There are {roleCount.Value} users with the role {roleCount.Key}");
}
输出:
There are 3 users with the role Admin
There are 2 users with the role Member
There are 1 users with the role Guest
虽然 LINQ 方法的第三方库提供了一些扩展功能,但这些方法正式包含在 .NET 9 Alpha 版本中标志着一个重要的里程碑。它标志着 Microsoft 致力于增强 LINQ 库本身,将这些强大且急需的功能直接集成到核心框架中,确保直接来自 .NET 生态系统的主要维护者的强大支持和优化
作者:Merwan Chinta 原文:https://medium.com/codenx/net9-alpha-linq-updates-c2df66d20e1b