C# 8 and .NET Core 3 – What's new?10TH ANNUAL CONFERENCE ABOUT MODERN IT TECHNOLOGIES Guidelines...

10TH ANNUAL CONFERENCE ABOUT MODERN IT TECHNOLOGIES

C# 8 and .NET Core 3 –What's new?


Topics

New C# 8 Features

.NET Core 3.0


Christian Nagel• Training• Coaching• Consulting• Development

• Microsoft MVP• www.cninnovation.com• csharp.christiannagel.com• github.com/christiannagel• github.com/cninnovation


DESKTOP WEB CLOUD MOBILE GAMING IoT AI

.NET

.NET Overview


.NET Core 3.0


Generic Host

• Dependency Injection Container• Configuration• Logging


Creating Windows Services

• UseWindowsService API• dotnet publish• sc create {Service} --binPath=<path to exe>


GRPC

• Binary Protocol• Protobuf• Using HTTP/2• Extensions for the .NET Toolchain


WPF

• .NET API Portability Analyzer• try-convert (unsupported tool)

• https://github.com/dotnet/try-convert• WPF Apps with .NET Core 3.0

https://github.com/dotnet/try-convert


.NET Core 3.0 – And more…

• ASP.NET Core Endpoint Routing• SignalR streaming from the client• EF Core Cosmos DB Provider• .NET Local Tools• Windows Native Interop• Create COM components• …


How to use C# 8


How to use C# 8

• By default enabled with .NET Core 3.0

• Enable with other projects• <LangVersion>8.0</LangVersion>• <Nullable>enable</Nullable>

• Directory.Build.Props


Features based on Frameworks/Runtimes

• Syntax sugar features with all frameworks• Some features based on classes & interfaces

• Ranges, async streams• Runtime updates required

• .NET Standard 2.1• Default Interface Members


Indices and Ranges


Indexes and Ranges

Index und Range & Types &

Extensions

New Operators• ^ Hat Operator• .. Range

Operator


Hat Operator

int[] arr = { 1, 2, 3 };int lastItem = arr[^1];


Range

string text1 = "the quick brown fox jumped over the lazy dogs";string quick = text1[4..9];string dog = text1[^4..^1];string brownfoxjumpedandmore = text1[10..];string thequick = text1[..8];string text2 = text1[..];


Demo

• Ranges and Indices

• Access Slice of Span<T>• Access String• Range, Index Types• Custom Collections


Implicit Support

Index• countable (Length, Count)• instance indexer with int

Range• countable• Slice method with two int


Nullable Reference Types


Null References

Most common .NET Exception

NullReferenceException

Billion Dollar Mistake

1965 in Algol by Tony Hoare

"Billion Dollar Mistake"


Null Conditional Operator (C# 6)

• Null checks made easier

int? length = customers?.Length;Customer first = customers?[0];int? count = customers?[0]?.Orders?.Count();

public void OnPropertyChanged([CallerMemberName] string propertyName = null) => PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));


Coalescing Operator (C# 5)

• Default values for null

int length = customers?.Length ?? 0;

public bool CanExecute(object parameter) => _canExecute?.Invoke() ?? true;


Reference Types are not

Nullable

• #nullable enable/disable/restore• annotated with ? – nullable reference type

• string?• Null-forgiving operator

• !• Null-coalescing assignment

• numbers ??= new List<string>();


Nullable Reference Types

• Documentation: null or not null• Helps finding bugs, no guarantees!• Flow analysis - tracks nullable reference variables• Breaks existing code (opt-in)• Nullability implemented with metadata (ignored

by down-level compilers)• string, T non-nullable• string?, T? nullable


Demo • Nullable Reference Types

• Enable nullability• Add annotations• Solving issues• Current issues


Guidelines

• Library authors – Nullable adoption phasebefore .NET 5

• App developers – nullability on your own pace

• Annotate new APIs• Do not remove argument validation• Parameter is non-nullable if parameters are

checked (ArgumentNullException)• Parameter is nullable if documented to

accept null• Prefer nullable over non-nullable with

disagreements


Async Streams


Async Streams

before C# 8: async/await returns one result

Async streams extends async/await with a stream of results

Asynchronous data source controlled by the consumer

Alternative to System.Reactive


Async Streams

• IAsyncDisposable• IAsyncEnumerable• IAsyncEnumerator

public interface IAsyncDisposable{ValueTask DisposeAsync();

}

public interface IAsyncEnumerable<out T>{IAsyncEnumerator<T> GetAsyncEnumerator();

}

public interface IAsyncEnumerator<out T> : IAsyncDisposable

{ValueTask<bool> MoveNextAsync();T Current { get; }

}


Using Async Streams

• await foreach

IAsyncEnumerator<T> enumerator = enumerable.GetAsyncEnumerator();

try{

while (await enumerator.MoveNextAsync()){

Use(enumerator.Current);}

}finally{

await enumerator.DisposeAsync();}

await foreach (var i in enumerable){Use(i);

}


Async with yield

• return IAsyncEnumerable

static async IAsyncEnumerable<int> MyIterator(){

try{

for (int i = 0; i < 100; i++){

await Task.Delay(1000);yield return i;

}}finally{

await Task.Delay(200);Console.WriteLine("finally");

}}


Demo

• Async Streams & SignalR

• Streaming from the Server to the Client• Streaming from the Client to the Server• C# 8 Async Streams


More Features…


using declaration

public void Method(IEnumerable<string> lines){using var file = new StreamWriter("sample.txt");foreach (var line in lines){file.WriteLine(line);

}}


switch Expression

static string M2(Shape shape) =>shape switch {

Shape s when s.Size.height > 100 =>$"large shape with size {s.Size} at position {s.Position}",

Ellipse e =>$"Ellipse with size {e.Size} at position {e.Position}",

Rectangle r =>$"Rectangle with size {r.Size} at position {r.Position}",

_ => "another shape" }

};


Recursive, Property, and Discard Patterns

static string M3(Shape shape) =>shape switch{CombinedShape (var shape1, var (pos, _)) => $"combined shape - shape1: {shape1.Name}, pos of shape2: {pos}",

{ Size: (200, 200), Position: var pos } => $"shape with size 200x200 at position {pos.x}:{pos.y}",

Ellipse (var pos, var size) => $"Ellipse with size {size} at position {pos}",

Rectangle (_, var size) => $"Rectangle with size {size}",_ => "another shape"

};


Demo• Switch expressions with tuples• Pattern matching


.NET Futures

.NET Core 3.1

Long-Term SupportDec-2019

.NET 5.0

CurrentNov-2020

.NET 6.0

LTSNov-2021


Questions?


For action

• Use .NET Core• Annotate libraries with nullability• Use new C# 8 features• Create Windows Services, use gRPC

• https://csharp.christiannagel.com• https://github.com/christiannagel/thriveconf2019• https://github.com/ProfessionalCSharp

https://csharp.christiannagel.com/

https://github.com/christiannagel/thriveconf2019

https://github.com/ProfessionalCSharp


THANK YOU


Thank you Sponsors #ThriveITconf

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Evening event sponsor

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C# 8 and .NET Core 3 – What's new?10TH ANNUAL CONFERENCE ABOUT MODERN IT TECHNOLOGIES Guidelines...

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