20 个 .NET 6 新增的 API

Posted 2022-01-06 dotNET跨平台

DateOnly & TimeOnly

.NET 6 引入了两种期待已久的类型 - DateOnly 和 TimeOnly, 它们分别代表DateTime的日期和时间部分。

DateOnly dateOnly = new(2021, 9, 25);Console.WriteLine(dateOnly);TimeOnly timeOnly = new(19, 0, 0);Console.WriteLine(timeOnly); DateOnly dateOnlyFromDate = DateOnly.FromDateTime(DateTime.Now);Console.WriteLine(dateOnlyFromDate); TimeOnly timeOnlyFromDate = TimeOnly.FromDateTime(DateTime.Now);Console.WriteLine(timeOnlyFromDate);

Parallel.ForEachAsync

它可以控制多个异步任务的并行度。

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, 在抛出异常之前不需要在每个方法中检查 null, 现在只需要写一行, 和 response.EnsureSuccessStatusCode(); 类似。

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

PriorityQueue

.NET 6 新增的数据结构, PriorityQueue, 队列每个元素都有一个关联的优先级，它决定了出队顺序, 编号小的元素优先出列。

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

RandomAccess

提供基于偏移量的 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 filebyte[] strBytes = Encoding.UTF8.GetBytes("Hello world");ReadOnlyMemory<byte> buffer1 = new(strBytes);await RandomAccess.WriteAsync(handle, buffer1, 0);// Get file lengthlong length = RandomAccess.GetLength(handle);// Read from fileMemory<byte> buffer2 = new(new byte[length]);await RandomAccess.ReadAsync(handle, buffer2, 0);string content = Encoding.UTF8.GetString(buffer2.ToArray());Console.WriteLine(content); // Hello world

PeriodicTimer

认识一个完全异步的“PeriodicTimer”, 更适合在异步场景中使用, 它有一个方法 WaitForNextTickAsync。

// 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// ...

Metrics API

.NET 6 实现了 OpenTelemetry Metrics API 规范, 内置了指标API, 通过 Meter 类创建下面的指标

•Counter•Histogram•ObservableCounter•ObservableGauge

使用的方法如下：

var builder = WebApplication.CreateBuilder(args);var app = builder.Build();// Create Metervar meter = new Meter("MetricsApp", "v1.0");// Create counterCounter<int> counter = meter.CreateCounter<int>("Requests");app.Use((context, next) =>    // Record the value of measurement    counter.Add(1);    return next(context););app.MapGet("/", () => "Hello World");StartMeterListener();app.Run();// Create and start Meter Listenervoid StartMeterListener()    var listener = new MeterListener();    listener.InstrumentPublished = (instrument, meterListener) =>            if (instrument.Name == "Requests" && instrument.Meter.Name == "MetricsApp")                    // Start listening to a specific measurement recording            meterListener.EnableMeasurementEvents(instrument, null);            ;    listener.SetMeasurementEventCallback<int>((instrument, measurement, tags, state) =>            Console.WriteLine($"Instrument instrument.Name has recorded the measurement: measurement");    );    listener.Start();

检查元素是否可为空的反射API

它提供来自反射成员的可空性信息和上下文：

•ParameterInfo 参数
•FieldInfo 字段
•PropertyInfo 属性
•EventInfo 事件

var example = new Example();var nullabilityInfoContext = new NullabilityInfoContext();foreach (var propertyInfo in example.GetType().GetProperties())    var nullabilityInfo = nullabilityInfoContext.Create(propertyInfo);    Console.WriteLine($"propertyInfo.Name property is nullabilityInfo.WriteState");// Output:// Name property is Nullable// Value property is NotNullclass Example    public string? Name  get; set;     public string Value  get; set; 

检查嵌套元素是否可为空的反射API

它允许您获取嵌套元素的可为空的信息, 您可以指定数组属性必须为非空，但元素可以为空，反之亦然。

Type exampleType = typeof(Example);PropertyInfo notNullableArrayPI = exampleType.GetProperty(nameof(Example.NotNullableArray));PropertyInfo nullableArrayPI = exampleType.GetProperty(nameof(Example.NullableArray));NullabilityInfoContext nullabilityInfoContext = new();NullabilityInfo notNullableArrayNI = nullabilityInfoContext.Create(notNullableArrayPI);Console.WriteLine(notNullableArrayNI.ReadState);              // NotNullConsole.WriteLine(notNullableArrayNI.ElementType.ReadState);  // NullableNullabilityInfo nullableArrayNI = nullabilityInfoContext.Create(nullableArrayPI);Console.WriteLine(nullableArrayNI.ReadState);                // NullableConsole.WriteLine(nullableArrayNI.ElementType.ReadState);    // Nullableclass Example    public string?[] NotNullableArray  get; set;     public string?[]? NullableArray  get; set; 

ProcessId & ProcessPath

直接通过 Environment 获取进程ID和路径。

int processId = Environment.ProcessIdstring path = Environment.ProcessPath;Console.WriteLine(processId);Console.WriteLine(path);

Configuration 新增 GetRequiredSection()

和 DI 的 GetRequiredService() 是一样的, 如果缺失, 则会抛出异常。

WebApplicationBuilder builder = WebApplication.CreateBuilder(args);WebApplication app = builder.Build();MySettings mySettings = new();// Throws InvalidOperationException if a required section of configuration is missingapp.Configuration.GetRequiredSection("MySettings").Bind(mySettings);app.Run();class MySettings    public string? SettingValue  get; set; 

CSPNG 密码安全伪随机数生成器

您可以从密码安全伪随机数生成器 (CSPNG) 轻松生成随机值序列。

它对于以下场景中很有用：

•密钥生成•随机数•某些签名方案中的盐

// Fills an array of 300 bytes with a cryptographically strong random sequence of values.// GetBytes(byte[] data);// GetBytes(byte[] data, int offset, int count)// GetBytes(int count)// GetBytes(Span<byte> data)byte[] bytes = RandomNumberGenerator.GetBytes(300);

Native Memory API

.NET 6 引入了一个新的 API 来分配本机内存, NativeMemory 有分配和释放内存的方法。

unsafe    byte* buffer = (byte*)NativeMemory.Alloc(100);    NativeMemory.Free(buffer);    /* This class contains methods that are mainly used to manage native memory.    public static class NativeMemory            public unsafe static void* AlignedAlloc(nuint byteCount, nuint alignment);        public unsafe static void AlignedFree(void* ptr);        public unsafe static void* AlignedRealloc(void* ptr, nuint byteCount, nuint alignment);        public unsafe static void* Alloc(nuint byteCount);        public unsafe static void* Alloc(nuint elementCount, nuint elementSize);        public unsafe static void* AllocZeroed(nuint byteCount);        public unsafe static void* AllocZeroed(nuint elementCount, nuint elementSize);        public unsafe static void Free(void* ptr);        public unsafe static void* Realloc(void* ptr, nuint byteCount);    */

Power of 2

.NET 6 引入了用于处理 2 的幂的新方法。

•'IsPow2' 判断指定值是否为 2 的幂。•'RoundUpToPowerOf2' 将指定值四舍五入到 2 的幂。

// IsPow2 evaluates whether the specified Int32 value is a power of two.Console.WriteLine(BitOperations.IsPow2(128));            // True// RoundUpToPowerOf2 rounds the specified T:System.UInt32 value up to a power of two.Console.WriteLine(BitOperations.RoundUpToPowerOf2(200)); // 256

WaitAsync on Task

您可以更轻松地等待异步任务执行, 如果超时会抛出 “TimeoutException”

Task operationTask = DoSomethingLongAsync();await operationTask.WaitAsync(TimeSpan.FromSeconds(5));async Task DoSomethingLongAsync()    Console.WriteLine("DoSomethingLongAsync started.");    await Task.Delay(TimeSpan.FromSeconds(10));    Console.WriteLine("DoSomethingLongAsync ended.");// Output:// DoSomethingLongAsync started.// Unhandled exception.System.TimeoutException: The operation has timed out.

新的数学API

新方法:

•SinCos•ReciprocalEstimate•ReciprocalSqrtEstimate

新的重载：

•Min, Max, Abs, Sign, Clamp 支持 nint 和 nuint•DivRem 返回一个元组, 包括商和余数。

// New methods SinCos, ReciprocalEstimate and ReciprocalSqrtEstimate// Simultaneously computes Sin and Cos(double sin, double cos) = Math.SinCos(1.57);Console.WriteLine($"Sin = sin\\nCos = cos");// Computes an approximate of 1 / xdouble recEst = Math.ReciprocalEstimate(5);Console.WriteLine($"Reciprocal estimate = recEst");// Computes an approximate of 1 / Sqrt(x)double recSqrtEst = Math.ReciprocalSqrtEstimate(5);Console.WriteLine($"Reciprocal sqrt estimate = recSqrtEst");// New overloads// Min, Max, Abs, Clamp and Sign supports nint and nuint(nint a, nint b) = (5, 10);nint min = Math.Min(a, b);nint max = Math.Max(a, b);nint abs = Math.Abs(a);nint clamp = Math.Clamp(abs, min, max);nint sign = Math.Sign(a);Console.WriteLine($"Min = min\\nMax = max\\nAbs = abs");Console.WriteLine($"Clamp = clamp\\nSign = sign");// DivRem variants return a tuple(int quotient, int remainder) = Math.DivRem(2, 7);Console.WriteLine($"Quotient = quotient\\nRemainder = remainder");// Output:// Sin = 0.9999996829318346// Cos = 0.0007963267107331026// Reciprocal estimate = 0.2// Reciprocal sqrt estimate = 0.4472135954999579// Min = 5// Max = 10// Abs = 5// Clamp = 5// Sign = 1// Quotient = 0// Remainder = 2

CollectionsMarshal.GetValueRefOrNullRef

这个是在字典中循环或者修改结可变结构体时用, 可以减少结构的副本复制, 也可以避免字典重复进行哈希计算，这个有点晦涩难懂，有兴趣的可以看看这个

https://github.com/dotnet/runtime/issues/27062

Dictionary<int, MyStruct> dictionary = new()     1, new MyStruct  Count = 100  ;int key = 1;ref MyStruct value = ref CollectionsMarshal.GetValueRefOrNullRef(dictionary, key);// Returns Unsafe.NullRef<TValue>() if it doesn't exist; check using Unsafe.IsNullRef(ref value)if (!Unsafe.IsNullRef(ref value))    Console.WriteLine(value.Count); // Output: 100    // Mutate in-place    value.Count++;    Console.WriteLine(value.Count); // Output: 101struct MyStruct    public int Count  get; set; 

ConfigureHostOptions

IHostBuilder 上的新 ConfigureHostOptions API, 可以更简单的配置应用。

public class Program    public static void Main(string[] args)            CreateHostBuilder(args).Build().Run();        public static IHostBuilder CreateHostBuilder(string[] args) =>        Host.CreateDefaultBuilder(args)            .ConfigureHostOptions(o =>                            o.ShutdownTimeout = TimeSpan.FromMinutes(10);            );

Async Scope

.NET 6 引入了一种新的CreateAsyncScope方法, 当您处理 IAsyncDisposable 的服务时现有的CreateScope方法会引发异常, 使用 CreateAsyncScope 可以完美解决。

await using var provider = new ServiceCollection()        .AddScoped<Example>()        .BuildServiceProvider();await using (var scope = provider.CreateAsyncScope())    var example = scope.ServiceProvider.GetRequiredService<Example>();class Example : IAsyncDisposable    public ValueTask DisposeAsync() => default;

加密类简化

•DecryptCbc•DecryptCfb•DecryptEcb•EncryptCbc•EncryptCfb•EncryptEcb

static byte[] Decrypt(byte[] key, byte[] iv, byte[] ciphertext)    using (Aes aes = Aes.Create())            aes.Key = key;        return aes.DecryptCbc(ciphertext, iv, PaddingMode.PKCS7);    

全文完...

作者: Oleg Kyrylchuk^[1]

原文: https://blog.okyrylchuk.dev/

相关链接

[1] Oleg Kyrylchuk: https://hashnode.com/@okyrylchuk