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Mark!20 個 .NET 6 新增的 API

.NET 6 引入了兩種期待已久的類型 - DateOnly 和 TimeOnly, 它們分別代表 DateTime 的日期和時間部分。

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 );

它可以控制多個異步任務的並行度。

var userHandlers = new []

{

"users/okyrylchuk" ,

"users/jaredpar" ,

"users/davidfowl"

};

using HttpClient client = new ()

{

BaseAddress = new Uri ( "" ),

};

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} Bio: {user.Bio} " );

});

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 的小改進, 在拋出異常之前不需要在每個方法中檢查 null, 現在只需要寫壹行, 和 response.EnsureSuccessStatusCode(); 類似。

ExampleMethod ( null );

void ExampleMethod ( object param )

{

ArgumentNullException . ThrowIfNull ( param );

// Do something

}

.NET 6 新增的數據結構, PriorityQueue, 隊列每個元素都有壹個關聯的優先級,它決定了出隊順序, 編號小的元素優先出列。

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

提供基於偏移量的 API,用於以線程安全的方式讀取和寫入文件。

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

// Write to file

byte [] strBytes = Encoding . UTF8 . GetBytes ( "Hello world" );

ReadOnlyMemory buffer1 = new ( strBytes );

await RandomAccess . WriteAsync ( handle , buffer1 , 0 );

// Get file length

long length = RandomAccess . GetLength ( handle );

// Read from file

Memory buffer2 = new ( new byte [ length ]);

await RandomAccess . ReadAsync ( handle , buffer2 , 0 );

string content = Encoding . UTF8 . GetString ( buffer2 . ToArray ());

Console . WriteLine ( content ); // Hello world

認識壹個完全異步的“PeriodicTimer”, 更適合在異步場景中使用, 它有壹個方法 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

// ...

.NET 6 實現了 OpenTelemetry Metrics API 規範, 內置了指標API, 通過 Meter 類創建下面的指標

?Counter

?Histogram

?ObservableCounter

?ObservableGauge

使用的方法如下:

var builder = WebApplication . CreateBuilder ( args );

var app = builder . Build ();

// Create Meter

var meter = new Meter ( "MetricsApp" , "v1.0" );

// Create counter

Counter counter = meter . CreateCounter ( "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 Listener

void 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 (( instrument , measurement , tags , state ) =>

{

Console . WriteLine ( $ "Instrument {instrument.Name} has recorded the measurement: {measurement}" );

});

listener . Start ();

}

它提供來自反射成員的可空性信息和上下文:

?ParameterInfo 參數

?FieldInfo 字段

?PropertyInfo 屬性

?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 NotNull

class Example

{

public string ? Name { get ; set ; }

public string Value { get ; set ; }

}

它允許您獲取嵌套元素的可為空的信息, 您可以指定數組屬性必須為非空,但元素可以為空,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 ); // NotNull

Console . WriteLine ( notNullableArrayNI . ElementType . ReadState ); // Nullable

NullabilityInfo nullableArrayNI = nullabilityInfoContext . Create ( nullableArrayPI );

Console . WriteLine ( nullableArrayNI . ReadState ); // Nullable

Console . WriteLine ( nullableArrayNI . ElementType . ReadState ); // Nullable

class Example

{

public string ?[] NotNullableArray { get ; set ; }

public string ?[]? NullableArray { get ; set ; }

}

直接通過 Environment 獲取進程ID和路徑。

int processId = Environment . ProcessId

string path = Environment . ProcessPath ;

Console . WriteLine ( processId );

Console . WriteLine ( path );

和 DI 的 GetRequiredService() 是壹樣的, 如果缺失, 則會拋出異常。

WebApplicationBuilder builder = WebApplication . CreateBuilder ( args );

WebApplication app = builder . Build ();

MySettings mySettings = new ();

// Throws InvalidOperationException if a required section of configuration is missing

app . Configuration . GetRequiredSection ( "MySettings" ). Bind ( mySettings );

app . Run ();

class MySettings

{

public string ? SettingValue { get ; set ; }

}

您可以從密碼安全偽隨機數生成器 (CSPNG) 輕松生成隨機值序列。

它對於以下場景中很有用:

?密鑰生成

?隨機數

?某些簽名方案

// 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 data)

byte [] bytes = RandomNumberGenerator . GetBytes ( 300 );

.NET 6 引入了壹個新的 API 來分配本機內存, NativeMemory 有分配和釋放內存的方法。

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 );

}*/

}

.NET 6 引入了用於處理 2 的冪的新方法。

?'IsPow2' 判斷指定值是否為 2 的冪。

?'RoundUpToPowerOf2' 將指定值四舍五入到 2 的冪。

// 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

您可以更輕松地等待異步任務執行, 如果超時會拋出 “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.

新方法:

?SinCos

?ReciprocalEstimate

?ReciprocalSqrtEstimate

新的重載:

?Min, Max, Abs, Sign, Clamp 支持 nint 和 nuint

?DivRem 返回壹個元組, 包括商和余數。

// New methods SinCos, ReciprocalEstimate and ReciprocalSqrtEstimate

// Simultaneously computes Sin and Cos

( double sin , double cos ) = Math . SinCos ( 1.57 );

Console . WriteLine ( $ "Sin = {sin} Cos = {cos}" );

// Computes an approximate of 1 / x

double 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} Max = {max} Abs = {abs}" );

Console . WriteLine ( $ "Clamp = {clamp} Sign = {sign}" );

// DivRem variants return a tuple

( int quotient , int remainder ) = Math . DivRem ( 2 , 7 );

Console . WriteLine ( $ "Quotient = {quotient} Remainder = {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

這個是在字典中循環或者修改結可變結構體時用, 可以減少結構的副本復制, 也可以避免字典重復進行哈希計算,這個有點晦澀難懂,有興趣的可以看看這個

/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 () 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: 101

}

struct MyStruct

{

public int Count { get ; set ; }

}

IHostBuilder 上的新 ConfigureHostOptions API, 可以更簡單的配置應用。

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 );

});

}

.NET 6 引入了壹種新的 CreateAsyncScope 方法, 當您處理 IAsyncDisposable 的服務時現有的 CreateScope 方法會引發異常, 使用 CreateAsyncScope 可以完美解決。

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 ;

}

?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 );

}

}