What's new in c# 10

.NET Conf Israel 2021
What’s new in C# 10
Moaid Hathot
Senior Software Engineer @ Microsoft | ex-Azure MVP
Moaid.Hathot@outlook.com
@MoaidHathot
https://moaid.codes
https://meetup.com/Code-Digest
Code.Digest | .NET Conf Israel 2021 | What’s new In C# 10

 Record structs
 Allow both assignment and declaration in the same deconstruction
 Global using directives
 File-scoped namespace declaration
 Improvements of structure types
 Interpolated string handlers
 Extended property patterns
 Improvements on lambda expressions
 Allow const interpolated strings
 Record types can seal ToString()
 Improved definite assignment
 Allow AsyncMethodBuilder attribute to methods
 CallerArgumentExpression attribute
 Enhanced #line pragma
C# 10 features

 .NET 6 SDK
 IDEs & Editors
 Visual Studio 2022
 RoslynPad
 LinqPad
 https://sharplab.io
Prerequisites

About Moaid Hathot
 Senior software Engineer @ Microsoft
 Ex-Azure MVP
 Software Craftsmanship advocate
 Clean Coder
 Co-Founder of Code.Digest();
 https://meetup.com/Code-Digest
Moaid Hathot

C# feature
Records Improvements

Records
public record Person
{
public string FirstName { get; init; }
public string LastName { get; init; }
}

Records
public record Person
{
}
var moaid = new Person { FirstName = "Moaid", LastName = "Hathot"};

Records
public class Person
{
}

Records
public class Person
{
public override bool Equals(object obj)
=> obj is Person other && string.Equals(FirstName, other.FirstName) && string.Equals(LastName, other.LastName);
public override int GetHashCode()
=> HashCode.Combine(FirstName, LastName);
}

Records
public class Person : IEquatable<Person>
{
=> Equals(obj as Person);
public bool Equals(Person other)
=> other is { } && (FirstName, LastName) == (other.FirstName, other.LastName);
}

Records
{
public override string ToString()
=> $"Person {{ FirstName: '{FirstName}', LastName: '{LastName}' }}";
}

Records
{
public static bool operator ==(Person first, Person second)
=> object.ReferenceEquals(first, second) || (first is { } && first.Equals(second));
public static bool operator !=(Person first, Person second)
=> !(first == second);
}

Records
{
public static bool operator ==(Person first, Person second)
=> object.ReferenceEquals(first, second) || (first is { } && first.Equals(second));
public static bool operator !=(Person first, Person second)
=> !(first == second);
public void Deconstruct(out string firstName, out string lastname)
=> (firstName, lastname) = (FirstName, LastName);
}

Records
public record Person(string FirstName, string LastName);

Records
var moaid = new Person("Moaid", "Hathot");

Records
var wifu = moaid with { FirstName = "Haneeni" };

Records
var clone = moaid with { };

Records
var clone = moaid with { };
var (firstName, lastName) = moaid;

Records
public record struct Person(string FirstName, string LastName);

Records
public record struct Person(string FirstName, string LastName);
public record class Person(string FirstName, string LastName);

Records
Console.WriteLine(moaid);

Records
Console.WriteLine(moaid); //Person { FirstName = Moaid, LastName = Hathot }

Records
public record Dev(string FirstName, string LastName, string stack) : Person(FirstName, LastName);

Records
var moaid2 = new Dev("Moaid", "Hathot", ".NET");
Console.WriteLine(moaid2);

Records

Records
Console.WriteLine(moaid2); //Dev { FirstName = Moaid, LastName = Hathot, stack = .NET }

Records
public record Person(string FirstName, string LastName)
{
{
return $"This person name is {FirstName} {LastName}";
}
}

Records
{
{
}
}

Records
{
{
}
}
Console.WriteLine(moaid); //This person name is Moaid Hathot

Records
{
{
}
}
Console.WriteLine(moaid2); //Dev { FirstName = Moaid, LastName = Hathot, stack = .NET }

Records
{
public sealed override string ToString()
{
}
}

Records
{
{
}
}

Records
{
{
}
}
Console.WriteLine(moaid2); //This person name is Moaid Hathot

C# feature
Improvements of structure types

Structs
struct Foo
{
public int Bar { get; set; }
public Foo()
{
Bar = 10;
}
}

Structs
struct Foo
{
public Foo()
{
Bar = 10;
}
}
var foo = new Foo();

Structs
struct Foo
{
public Foo()
{
Bar = 10;
}
}
var foo = new Foo();
var baz = foo with { Bar = 100 };

Anonymous Types
var moaid = new { FirstName = "Moaid", LastName = "Hathot" };

C# feature
Deconstruction Improvements

ValueTuple Deconstruction
record Person(string FirstName, string LastName);

Person moaid = new ("Moaid", "Hathot");

Person moaid = new ("Moaid", "Hathot");
var (firstName, lastName) = moaid;

public class Person(string FirstName, string LastName);

public class Person(string FirstName, string LastName)
{
public void Deconstruct(out string firstName, out string lastName)
{
firstName = FirstName;
lastName = LastName;
}
}

var (firstName, lastName) = default;

string (foo, bar) = default;

int (foo, bar) = default;

int (foo, bar) = default;
(int foo, string bar) = default;

string (firstName, lastName) = default;

string firstName2;
string lastName2;
(firstName2, lastName2) = default;

string firstName2;
string lastName2;
(firstName2, lastName2) = default;
string lastName3;
(var firstName3, lastName3) = default;

C# feature
Extended Property Patterns

Extended property patterns
string obj = null;

string obj = null;
if (obj is { })
{
Console.WriteLine(obj);
}

string obj = null;
if (obj is { Length: var length })
{
Console.WriteLine(length);
}

string obj = null;
if (obj is { Length: 10 })
{
Console.WriteLine(10);
}

string obj = null;
if (obj is { Length: > 3 })
{
Console.WriteLine("> 3");
}

if (moaid is { FirstName: { Length: > 3 } })
{
}

if (moaid is { FirstName: { Length: > 3 } })
{
}
if (moaid is { FirstName.Length: > 3 })
{
}

C# features
Improvements on Lambda expressions

Lambda Improvements
var action = () => { };
var func = () => 5;

Lambda Improvements
var action = () => { };
var func = () => 5;
Action action = () => { };
Func<int> func = () => 5;

Lambda Improvements
var action = () => { };

Lambda Improvements
var action = () => { };
Action? action = () => { };

Lambda Improvements
var action = () => { };
var action2 = (string s) => { };

Lambda Improvements
var action = () => { };
var action2 = (string s) => { };
Action<string>? action2 = (string s) => { };

Lambda Improvements
var func = () => 5;

Lambda Improvements
var func = () => 5;
Func<int> func = () => 5;

Lambda Improvements
var func = int () => 5;
Func<int> func = int () => 5;

Lambda Improvements
var func = int () => 5;
var func = [FromBody] int () => 5;

C# features
Constant interpolated strings

const string Prefix = "https://";
const string Suffix = ".domain.com";

const string globalSrvice = Prefix + "dotnetconf" + Suffix;

const string globalSrvice = Prefix + "dotnetconf" + Suffix;
const string localService = $"{Prefix}dotnetconf-israel{Suffix}";

C# features
File-Scoped namespace
Global usings Directives

File-scoped namespace
using System;
namespace DotNetConf2021
{
public class Program
{
public static void Main()
{
Console.WriteLine("Hello World!");
}
}
}

namespace DotNetConf2021;
using System;
{
{
}
}

using System;

Global using Directive
using System;
namespace DotNetConf2021
{
{
{
}
}
}

using System;
using System.Linq;
using System.Collections.Generic;
using System.Threading;
using System.Threading.Tasks;

using System;
using System.Linq;
using System.Collections.Generic;
using System.Threading;
using System.Threading.Tasks;
using Human = DotNetConf2021.Person;

global using System;
global using System.Linq;
global using System.Collections.Generic;
global using System.Threading;
global using System.Threading.Tasks;
global using Human = DotNetConf2021.Person;

Best of //Build 2021
Questions?
Moaid Hathot
Senior Software Engineer @ Microsoft | ex-Azure MVP
Moaid.Hathot@outlook.com
@MoaidHathot
https://moaid.codes
https://meetup.com/Code-Digest

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