[译]. NET 6 新增API - 上

介绍

接下来我将给大家重点介绍一下.Net 6 之后的一些新的变更，文章都是来自于外国大佬的文章，我这边进行一个翻译，并加上一些自己的理解和解释。

源作者链接：https://blog.okyrylchuk.dev/20-new-apis-in-net-6#heading-a-new-periodictimer

正文

DateOnly and TimeOnly

.NET 6 引入了两种期待已久的类型 - DateOnly和TimeOnly。它们代表DateTime的日期或时间部分。

// public DateOnly(int year, int month, int day)
// public DateOnly(int year, int month, int day, Calendar calendar)
DateOnly dateOnly = new(2021, 9, 25);
Console.WriteLine(dateOnly);
// Output: 25-Sep-21

// public TimeOnly(int hour, int minute)
// public TimeOnly(int hour, int minute, int second)
// public TimeOnly(int hour, int minute, int second, int millisecond)
// public TimeOnly(long ticks)
TimeOnly timeOnly = new(19, 0, 0);
Console.WriteLine(timeOnly);
// Output: 19:00 PM

DateOnly dateOnlyFromDate = DateOnly.FromDateTime(DateTime.Now);
Console.WriteLine(dateOnlyFromDate);
// Output: 23-Sep-21

TimeOnly timeOnlyFromDate = TimeOnly.FromDateTime(DateTime.Now);
Console.WriteLine(timeOnlyFromDate);
// Output: 21:03 PM

Parallel.ForEachAsync

它允许您控制计划异步工作的并行度。

var userHandlers = new[]
{
    "users/okyrylchuk",
    "users/jaredpar",
    "users/davidfowl"
};

using HttpClient client = new()
{
    BaseAddress = new Uri("https://api.github.com"),
};
client.DefaultRequestHeaders.UserAgent.Add(new ProductInfoHeaderValue("DotNet", "6"));

ParallelOptions options = new()
{
    MaxDegreeOfParallelism = 3
};
await Parallel.ForEachAsync(userHandlers, options, async (uri, token) =>
{
    var user = await client.GetFromJsonAsync<GitHubUser>(uri, token);
    Console.WriteLine($"Name: {user.Name}\nBio: {user.Bio}\n");
});

public class GitHubUser
{
    public string Name { get; set; }
    public string Bio { get; set; }
}

// Output:
// Name: David Fowler
// Bio: Partner Software Architect at Microsoft on the ASP.NET team, Creator of SignalR
// 
// Name: Oleg Kyrylchuk
// Bio: Software developer | Dotnet | C# | Azure
// 
// Name: Jared Parsons
// Bio: Developer on the C# compiler

ArgumentNullException.ThrowIfNull()

ArgumentNullException 的小改进。在抛出异常之前，无需在每个方法中检查 null。

ExampleMethod(null);

void ExampleMethod(object param)
{
    ArgumentNullException.ThrowIfNull(param);
    // Do something
}

PriorityQueue

在 .NET 6 中遇到一种新的数据结构。PriorityQueue 表示最小优先级队列。每个元素都使用确定出队顺序的关联优先级入队。编号最小的元素首先出列。

PriorityQueue<string, int> priorityQueue = new();

priorityQueue.Enqueue("Second", 2);
priorityQueue.Enqueue("Fourth", 4);
priorityQueue.Enqueue("Third 1", 3);
priorityQueue.Enqueue("Third 2", 3);
priorityQueue.Enqueue("First", 1);

while (priorityQueue.Count > 0)
{
    string item = priorityQueue.Dequeue();
    Console.WriteLine(item);
}

// Output:
// First
// Second
// Third 2
// Third 1
// Fourth

Reading and Writing Files

.NET 6 引入了一个新的低级 API，用于在没有 FileStream 的情况下读取和写入文件。一种新类型 RandomAccess 提供了基于偏移量的 API，用于以线程安全的方式读取和写入文件。

using SafeFileHandle handle = File.OpenHandle("file.txt", access: FileAccess.ReadWrite);

// Write to file
byte[] strBytes = Encoding.UTF8.GetBytes("Hello world");
ReadOnlyMemory<byte> buffer1 = new(strBytes);
await RandomAccess.WriteAsync(handle, buffer1, 0);

// Get file length
long length = RandomAccess.GetLength(handle);

// Read from file
Memory<byte> buffer2 = new(new byte[length]);
await RandomAccess.ReadAsync(handle, buffer2, 0);
string content = Encoding.UTF8.GetString(buffer2.ToArray());
Console.WriteLine(content); // Hello world

A New PeriodicTimer

满足一个完全异步的“PeriodicTimer”。它允许异步等待计时器滴答声。它有一个方法，“WaitForNextTickAsync”，它等待计时器的下一个滴答声或计时器停止。

// One constructor: public PeriodicTimer(TimeSpan period)
using PeriodicTimer timer = new(TimeSpan.FromSeconds(1));

while (await timer.WaitForNextTickAsync())
{
    Console.WriteLine(DateTime.UtcNow);
}

// Output:
// 13 - Oct - 21 19:58:05 PM
// 13 - Oct - 21 19:58:06 PM
// 13 - Oct - 21 19:58:07 PM
// 13 - Oct - 21 19:58:08 PM
// 13 - Oct - 21 19:58:09 PM
// 13 - Oct - 21 19:58:10 PM
// 13 - Oct - 21 19:58:11 PM
// 13 - Oct - 21 19:58:12 PM
// ...

结语

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