1. DateOnly & TimeOnly
NET 6 introduces two long-awaited types- DateOnly and TimeOnly, which represent the date and time portions of DateTime, respectively.
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);
2. Parallel.ForEachAsync
It can control the parallelism of multiple asynchronous tasks.
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
3. 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
}
4. 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
5. RandomAccess
Provides offset-based APIs for reading and writing files in a thread-safe manner.
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
6. 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
// ...
7. 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
The methods used are as follows:
var builder = WebApplication.CreateBuilder(args);
var app = builder.Build();
// Create Meter
var meter = new Meter("MetricsApp", "v1.0");
// Create counter
Counter<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 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<int>((instrument, measurement, tags, state) =>
{
Console.WriteLine($"Instrument {instrument.Name} has recorded the measurement: {measurement}");
});
listener.Start();
}
8. Reflection API to check if an element is nullable
It provides nullability information and context from reflection members:
- ParameterInfo parameter
- FieldInfo field
- PropertyInfo property
- EventInfo event
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; }
}
9. Reflection API to check whether nested elements can be nullable
It allows you to get nullable information about nested elements, and you can specify that array attributes must be non-nullable, but elements can be nullable, and vice versa.
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; }
}
10. ProcessId & ProcessPath
Get the process ID and path directly through the Environment.
int processId = Environment.ProcessId
string path = Environment.ProcessPath;
Console.WriteLine(processId);
Console.WriteLine(path);
11. Configuration adds 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 missing
app.Configuration.GetRequiredSection("MySettings").Bind(mySettings);
app.Run();
class MySettings
{
public string? SettingValue { get; set; }
}
12. CSPNG Cryptographic Security Pseudo-random Number Generator
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。
It is useful in the following scenarios:
- key generation
- random number
- Salt in certain signature schemes
// 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);
13. 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);
}*/
}
14. Power of 2
NET 6 introduces a new method for handling powers of 2.
- 'IsPow2' determines whether the specified value is a power of 2.
- 'RoundUpToPowerOf2' rounds the specified value to a power of 2.
// 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
15. WaitAsync on Task
You can more easily wait for asynchronous tasks to execute, and a "TimeoutException" will be thrown if it times out
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.
16. New Mathematics API
New method:
- SinCos
- ReciprocalEstimate
- ReciprocalSqrtEstimate
New overload:
- Min, Max, Abs, Sign, Clamp support nint and nuint
- DivRem returns a tuple including the quotient and remainder.
// 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
17. CollectionsMarshal.GetValueRefOrNullRef
This is used when cycling or modifying variable structures in the dictionary. It can reduce the duplication of copies of structures and avoid repeated hash calculations in the dictionary. This is a bit obscure. If you are interested, you can take a look at this.
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; }
}
18. 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);
});
}
19. 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;
}
20. Encryption simplification
- 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);
}
}
End of the full text...
作者: Oleg Kyrylchuk