[译]. NET 6 新增API

Posted 2022-01-17 初久的私房菜

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

Power of 2

.NET 6 引入了使用 2 的幂的新助手。

• \'IsPow2\' 评估指定值是否为 2 的幂。
• \'RoundUpToPowerOf2\' 如果超过了最大值，即2的30此幂，将设置成最大值，如果这个数的二进制是零的话返回1，即输入0返回1。

// 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

等待异步任务

您可以更轻松地等待任务异步完成执行。操作超时时抛出“TimeoutException”。

⚠️这是不可取消的操作！

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 supports nint and nuint
• DivRem variants return a tuples

// 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 / 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($"Min = min\\nMax = max\\nAbs = abs");
Console.WriteLine($"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

它返回一个可以就地更新的结构值的引用。它不是用于一般用途，而是用于高性能场景。

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; set; 

配置主机选项

IHostBuilder 上的新 ConfigureHostOptions API。它使应用程序设置更简单。

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);
            );

创建异步范围

.NET 6 引入了一个新的CreateAsyncScope方法来创建AsyncServiceScope。处置IAsyncDisposable服务时，现有的CreateScope方法会引发异常。CreateAsyncScope提供了一个简单的解决方案。

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;

加密操作的简化调用模式

SymmetricAlgorithm上的新方法可在有效负载已在内存中时避免流：

• 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);
    

结语

联系作者：加群：867095512 @MrChuJiu