.NET 6新增的20个API介绍

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 urhandlers = new[]{    "urs/okyrylchuk",    "urs/jaredpar",    "urs/davidfowl"};using httpclient client = new(){    baaddress = new uri("https://api.github.com"),};client.defaultrequestheaders.uragent.add(new productinfoheadervalue("dotnet", "6"));paralleloptions options = new(){    maxdegreeofparallelism = 3};await parallel.foreachasync(urhandlers, options, async (uri, token) =>{    var ur = await client.getfromjsonasync<githubur>(uri, token);    console.writeline($"name: {ur.name}\nbio: {ur.bio}\n");});public class githubur{    public string name { get; t; }    public string bio { get; t; }}// output:// name: david fowler// bio: partner software arc激励自己努力的句子hitect 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 respon.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("cond", 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// cond// 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.fromconds(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

counterhistogramobrvablecounterobrvablegauge

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.u((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.tmeasurementeventcallback<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; t; }    public string value { get; t; }}

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; t; }    public string?[]? nullablearray { get; t; }}

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 getrequiredction()

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

webapplicationbuilder builder = webapplication.createbuilder(args);webapplication app = builder.build();myttings myttings = new();// throws invalidoperationexception if a required ction of configuration is missingapp.configuration.getrequiredction("myttings").bind(myttings);app.run();class myttings{    public string? ttingvalue { get; t; }}

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 quence of values.// getbytes(byte[] data);// getbytes(byte[] data, int offt, 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 ud to manage native memory.    public static class nativememory    {    电脑发射wifi    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.fromconds(5));async task dosomethinglongasync(){    console.writeline("dosomethinglongasync started.");    await task.delay(timespan.fromconds(10));    console.writeline("dosomethinglongasync ended.");}// outpuchina11boysvideos国产t:// dosomethinglongasync started.// unhandled exception.system.timeoutexception: the operation has timed out.

新的数学api

新方法:

sincosreciprocalestimatereciprocalsqrtestimate

新的重载：

min, max, abs, sign, clamp 支持 nint 和 nuintdivrem 返回一个元组, 包括商和余数。

// new methods sincos, re大西国ciprocalestimate 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: 101}struct mystruct{    public int count { get; t; }}

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 rvicecollection()        .addscoped<example>()        .buildrviceprovider();await using (var scope = provider.createasyncscope()){    var example = scope.rviceprovider.getreq我可能不会爱你经典台词uiredrvice<example>();}class example : iasyncdisposable{    public valuetask dispoasync() => default;}

加密类简化

decryptcbcdecryptcfbdecryptecbencryptcbcencryptcfbencryptecb

static byte[] decrypt(byte[] key, byte[] iv, byte[] ciphertext){    using (aes aes = aes.create())    {        aes.key = key;        return aes.decryptcbc(ciphertext, iv, paddingmode.pkcs7);    }}

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