1. C# 6.0 April 2014 Preview
Paulo Morgado
http://netponto.org47ª Reunião Lisboa - 31/05/2014

2. Who Am I?
Paulo Morgado
CodePlex
Revista
PROGRAMAR

3. Agenda
• C# Evolution
• .NET Compiler Platform (“Roslyn”)
• C# 6.0 Features
• Demos

4. C# 1.0
Managed
C# 2.0
Generics
C# 3.0
LINQ
C# 4.0
Dynamic
Programming
C# 5.0
Asynchronous
Programming
Windows Runtime
C# 6.0
Compiler Platform
“Roslyn”
C# Evolution

5. .NET Compiler Platform (“Roslyn”)
A reimplementation of C# and VB compilers
In C# and VB
With rich public APIs
On CodePlex

6. Why “Roslyn”?

7. C# 6.0 Features
Disclaimer:
At this point, some of the features are
implemente, others are planned and others
are being considered.

8. public class Customer
{
public string FirstName { get; private set; }
public string LastName { get; private set; }
}
public class Customer
{
public string FirstName { get; private set; } = "John";
public string LastName { get; private set; } = "Doe";
}
Auto-Property Initializers
public class Customer
{
public string FirstName { get; } = "John";
public string LastName { get; } = "Doe";
}

9. Primary Constructors
Class and Struct Parameters
public class Customer
{
private string firstName;
private string lastName;
public Customer(string firstName, string lastName)
{
this.nome = firstName;
this.lastName = lastName;
}
public string FirstName { get { return firstName; } }
public string LastName { get { return lastName; } }
}
public class Customer
{
private string firstName;
private string lastName;
public Customer(string firstName, string lastName)
{
this.nome = firstName;
this.lastName = lastName;
}
public string FirstName { get { return firstName; } }
public string LastName { get { return lastName; } }
}
public class Customer(string firstName, string lastName)
{
public string FirstName { get; } = firstName;
public string LatName { get; } = lastName;
}

10. Primary Constructors
Field Parameters
public class Customer(
string firstName,
string lastName,
DateTime birthDate)
{
public string FirstName { get; } = firstName;
public string LatName { get; } = lastName;
private DateTime _birthDate = birthDate;
}
public class Customer(
string firstName,
string lastName,
DateTime birthDate)
{
public string FirstName { get; } = firstName;
public string LatName { get; } = lastName;
private DateTime _birthDate = birthDate;
}
public class Customer(
string firstName,
string lastName,
private DateTime birthDate)
{
public string FirstName { get; } = firstName;
public string LatName { get; } = lastName;
}
public class Customer(
string firstName,
string lastName,
private DateTime birthDate)
{
public string FirstName { get; } = firstName;
public string LatName { get; } = lastName;
public int Age
{
get { return CalcularAge(birthDate); }
}
}

11. Primary Constructors
Explicit Constructors
public Point()
: this(0, 0) // calls the primary constructor
{
}

12. Primary Constructors
Base Initializer
class BufferFullException()
: Exception("Buffer full")
{
}

13. Primary Constructors
Partial Types
If a class is declared in multiple parts, only one
of those parts can declare a constructor
parameters and only that part can declare
parameters on the specification of the base
class.

14. Using Static
using System;
class Program
{
static void Main()
{
Console.WriteLine(Math.Sqrt(3 * 3 + 4 * 4));
}
}
using System;
class Program
{
static void Main()
{
Console.WriteLine(Math.Sqrt(3 * 3 + 4 * 4));
}
}
using System.Console;
using System.Math;
class Program
{
static void Main()
{
WriteLine(Sqrt(3 * 3 + 4 * 4));
}
}

15. Using Static
Extension Methods
using System.Linq.Enumerable; // Just the type, not the whole namespace
class Program
{
static void Main()
{
var range = Range(5, 17);
var odd = Where(range, i => i % 2 == 1);
var even = range.Where(i => i % 2 == 0);
}
}
using System.Linq.Enumerable; // Just the type, not the whole namespace
class Program
{
static void Main()
{
var range = Range(5, 17); // Allowed
var odd = Where(range, i => i % 2 == 1); // Not Allowed
var even = range.Where(i => i % 2 == 0); // Allowed
}
}

16. Declaration Expressions
if (int.TryParse(s, out int i)) { … }
GetCoordinates(out var x, out var y);
Console.WriteLine("Result: {0}", (int x = GetValue()) * x);
if ((string s = o as string) != null) { … s … }
from s in strings
select int.TryParse(s, out int i) ? i : -1;

17. Excpetion Filters
try
{
…
}
catch (Exception e) if (myfilter(e))
{
…
}

18. Binary Literals
var bits = 0b00101110;

19. Digit Separators
var bits = 0b0010_1110;
var hex = 0x00_2E;
var dec = 1_234_567_890;

20. Extension Add Methods in Collection
Initializers
On the first implementation of collection initializers in C#,
the Add methods that get called couldn’t be extension
methods.
VB got it right from the start, but it seems C# had been
forgoten.
This has been fixed: the code generated from a collection
initializer will now happily call an extension method called
Add.
It’s not much of a feature, but it’s occasionally useful, and it
turned out implementing it in the new compiler amounted
to removing a check that prevented it.

21. Element Initializers
var numbers = new Dictionary<int, string>
{
[7] = “seven",
[9] = “nine",
[13] = “thirteen"
};

22. Indexed Members
var customer = new JsonData
{
$first = "Anders", // => ["first"] = "Anders"
$last = "Hejlsberg" // => ["last"] = "Hejlsberg"
};
string first = customer.$first; // => customer["first"]

23. Await in catch and finally blocks
Resource res = null;
try
{
// You could do this.
res = await res.OpenAsync(…);
…
}
catch (ResourceException e)
{
// Now you can do this …
await res.LogAsync(res, e);
}
finally
{
// … and this.
if (res != null) await res.CloseAsync();
}

24. Expression-Bodied Members
public class Point(int x, int y)
{
public int X => x;
public int Y => y;
public double Dist => Math.Sqrt(x* x + y* y);
public Point Move(int dx, int dy) => new Point(x + dx, y + dy);
}

25. Event Initializers
var button = new Button
{
...
Click += (source, e) => ...
...
};

26. Semicolon Operator
(var x = Foo(); Write(x); x*x)

27. Params IEnumerable
int Avg(params IEnumerable<int> numbers) { … }

28. String Interpolation
"{p.First} {p.Last} is {p.Age} years old."
discussion

29. NameOf Operator
string s = nameof(Console.Write);

30. Null Propagation
var temp = GetCustomer();
string name = (temp == null) ? null : temp.Name;
var temp = GetCustomer()?.Name;

31. Null Propagation
Associativity
– Left associative
• ((a?.b)?.c)
– Right associative
• (a?.(b?.c))
int? l = customer?.Nome.Length;
discussion

32. Protected and Internal
protected internal
protected internal
protectedinternal
discussion

33. Questions?

35. Call to action
• Use the IDE and language features
• Dip your toes in custom diagnostics
• Consider forking the compiler source
• Give feedback

36. References
MSDN
– http://www.msdn.com/roslyn
Download Preview
– http://aka.ms/Roslyn
CodePlex
– http://roslyn.codeplex.com/
Roslyn source browser
– http://source.roslyn.codeplex.com/

37. References
The Future of C# - //build/ 2014
– http://channel9.msdn.com/Events/Build/2014/2-577
What’s New for C# Developers - //build/ 2014
– http://channel9.msdn.com/Events/Build/2014/9-020
Anders Hejlsberg Live Q&A - //build/ 2014
– http://channel9.msdn.com/Events/Build/2014/9-010
The Future of Visual Basic and C# - TechEd North America 2014
– http://channel9.msdn.com/Events/TechEd/NorthAmerica/2014/DEV-B336
Channel 9 Live: .NET Framework Q&A - TechEd North America 2014
– http://channel9.msdn.com/Events/TechEd/NorthAmerica/2014/C9-22

38. References
C# – Novas Funcionalidades do C# 6.0 – Antevisão de Abril de 2014
– http://www.revista-programar.info/artigos/c-novas-funcionalidades-do-c-6-0-antevisao-de-abril-
de-2014/
A C# 6.0 Language Preview
– http://msdn.microsoft.com/en-us/magazine/dn683793.aspx

39. Questões?

40. Obrigado!
Paulo Morgado
http://PauloMorgado.NET/
https://twitter.com/PauloMorgado
https://www.facebook.com/PauloMorgado.NET
http://www.slideshare.net/PauloJorgeMorgado

41. Patrocinadores “GOLD”
Twitter: @PTMicrosoft http://www.microsoft.com/portugal

42. Patrocinadores “Silver”

43. Patrocinadores “Bronze”

44. http://bit.ly/netponto-aval-47
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iremos enviar um email com o link à tarde

45. Próximas reuniões presenciais
31/05/2014 – Maio (Lisboa)
21/06/2014 – Junho (Lisboa)
27/07/2014 – Julho (Lisboa)
??/??/???? – ????? (Porto)
Reserva estes dias na agenda! :)