A look into what came after C# 7.0 and what's coming in C# 8.0.

3. Paulo Morgado
• PauloMorgado.NET
• @PauloMorgado
• github.com/paulomorgado
• stackoverflow.com/users/402366/paulo-morgado
• slideshare.net/PauloJorgeMorgado
• www.facebook.com/paulomorgado.net
• revista-programar.info/author/pmorgado/
• luisabreu.github.io/csharp7pt/
• www.fca.pt/pt/catalogo-
pesquisa/?filtros=2&q=Paulo+Morgado

4. static async Task Main(string[] args)
{
int[] numbers = { 0b1, 0b10, 0b100, 0b1000, 0b1_0000, 0b10_0000 };
int result = await SumOfSquaresAsync(numbers);
WriteLine(result);
}
static Task<int> SumOfSquaresAsync(int[] numbers)
=> Task.FromResult(numbers.Select(i => i * i).Sum());
static async Task<int> Main(string[] args)
https://docs.microsoft.com/en-us/dotnet/csharp/whats-new/csharp-7-1#async-main
https://github.com/dotnet/csharplang/blob/master/proposals/csharp-7.1/async-main.md

5. https://docs.microsoft.com/en-us/dotnet/csharp/whats-new/csharp-7-1#default-literal-expressions
https://github.com/dotnet/csharplang/blob/master/proposals/csharp-7.1/target-typed-default.md
int result = await SumOfSquaresAsync(numbers, default(CancellationToken));int result = await SumOfSquaresAsync(numbers, default);

6. int count = 5;
string label = "Colors used in the map";
var pair = (count: count, label: label);
int count = 5;
string label = "Colors used in the map";
var pair = (count, label); // element names are "count" and "label"
https://docs.microsoft.com/en-us/dotnet/csharp/whats-new/csharp-7-1#inferred-tuple-element-names
https://github.com/dotnet/csharplang/blob/master/proposals/csharp-7.1/infer-tuple-names.md

7. /refout /refonly
https://docs.microsoft.com/en-us/dotnet/csharp/whats-new/csharp-7-1#async-main
https://github.com/dotnet/csharplang/blob/master/proposals/csharp-7.1/async-main.md

8. https://docs.microsoft.com/en-us/dotnet/csharp/whats-new/csharp-7-2#non-trailing-named-arguments
https://github.com/dotnet/csharplang/blob/master/proposals/csharp-7.2/non-trailing-named-arguments.md
void M(int arg1, string arg2, bool arg3 = false);
M(1, arg2: "s", true); // valid in C# 7.3
M(arg2: "s", 0); // not valid
M(arg2: "s", 0, arg3: true); // not valid

9. https://docs.microsoft.com/en-us/dotnet/csharp/whats-new/csharp-7-2#leading-underscores-in-numeric-literals
https://github.com/dotnet/roslyn/pull/20449
var b = 0b_1111_0000;
var h = 0x_FF_00;

10. ref T Choice<T>(bool condition, ref T consequence, ref T alternative)
{
if (condition)
{
return ref consequence;
}
else
{
return ref alternative;
}
}
https://github.com/dotnet/csharplang/blob/master/proposals/csharp-7.2/conditional-ref.md
ref T Choice<T>(bool condition, ref T consequence, ref T alternative)
{
return ref condition ? ref consequence : ref alternative;
}

11. https://docs.microsoft.com/en-us/dotnet/csharp/whats-new/csharp-7-2#private-protected-access-modifier
https://github.com/dotnet/csharplang/blob/master/proposals/csharp-7.2/private-protected.md

12. https://docs.microsoft.com/en-us/dotnet/csharp/whats-new/csharp-7-2#reference-semantics-with-value-types
https://github.com/dotnet/csharplang/blob/master/proposals/csharp-7.2/readonly-ref.md

13. // initialization
ref VeryLargeStruct refLocal = ref veryLargeStruct;
// reassigned, refLocal refers to different storage.
refLocal = ref anotherVeryLargeStruct;
https://docs.microsoft.com/en-us/dotnet/csharp/whats-new/csharp-7-3#ref-local-variables-may-be-reassigned

14. void M!<D>(D d) where D : Delegate { }
void M2<E>(E e) where E : Enum { }
unsafe void M3<T>(T *p) where T : unmanaged { }
https://docs.microsoft.com/en-us/dotnet/csharp/whats-new/csharp-7-3#enhanced-generic-constraints

15. var tuple = ("", 10);
if (tuple == ("", 10)) // true
if (("", 10) == (null, 5.2)) // false
if (("", 1, true) == (false, 5))
/*
Error CS8384
Tuple types used as operands of an == or != operator must have matching
cardinalities. But this operator has tuple types of cardinality 3 on the left
and 2 on the right.
*/
https://docs.microsoft.com/en-us/dotnet/csharp/whats-new/csharp-7-3#tuples-support--and-
https://github.com/dotnet/csharplang/issues/190

16. public class B
{
public B(int i, out int j) => j = i;
}
public class D : B
{
public D(int i) : base(i, out var j)
{
WriteLine($"The value of 'j' is {j}");
}
}
https://docs.microsoft.com/en-us/dotnet/csharp/whats-new/csharp-7-3#extend-expression-variables-in-initializers
https://github.com/dotnet/csharplang/blob/master/proposals/csharp-7.3/expression-variables-in-initializers.md

17. [field: SomeThingAboutFieldAttribute]
public int SomeProperty { get; set; }
https://docs.microsoft.com/en-us/dotnet/csharp/whats-new/csharp-7-3#attach-attributes-to-the-backing-fields-for-auto-implemented-properties
https://github.com/dotnet/csharplang/issues/42

18. int* pArr = stackalloc int[3] { 1, 2, 3 };
int* pArr2 = stackalloc int[] { 1, 2, 3 };
Span<int> arr = stackalloc[] { 1, 2, 3 };
https://docs.microsoft.com/en-us/dotnet/csharp/whats-new/csharp-7-3#stackalloc-arrays-support-initializers
https://github.com/dotnet/csharplang/issues/1286

19. unsafe struct S
{
public fixed int myFixedField[10];
}
class C
{
static S s = new S();
unsafe public void M()
{
fixed (int* ptr = s.myFixedField)
{
int p = ptr[5];
}
}
}
unsafe struct S
{
public fixed int myFixedField[10];
}
class C
{
static S s = new S();
unsafe public void M()
{
int p = s.myFixedField[5];
}
}
https://docs.microsoft.com/en-us/dotnet/csharp/whats-new/csharp-7-3#indexing-fixed-fields-does-not-require-pinning
https://github.com/dotnet/csharplang/blob/master/proposals/csharp-7.3/indexing-movable-fixed-fields.md

20. https://docs.microsoft.com/en-us/dotnet/csharp/whats-new/csharp-7-3#more-types-support-the-fixed-statement
https://github.com/dotnet/csharplang/issues/1314

21. https://docs.microsoft.com/en-us/dotnet/csharp/whats-new/csharp-7-3#improved-overload-candidates
https://github.com/dotnet/csharplang/issues/98

22. https://github.com/dotnet/csharplang/blob/master/proposals/nullable-reference-types.md
string? n = "world";
var x = b ? "Hello" : n; // string?
var y = b ? "Hello" : null; // string? or error
var z = b ? 7 : null; // Error today, could be int?

23. https://github.com/dotnet/roslyn/blob/features/range/docs/features/range.md
var slice = array[4..10];
switch (x)
{
case 0..10:
break;
}
foreach (var i in 0..10)
{
WriteLine(string.Join(",", (0..i).Select(j => i * j)));
}

24. https://github.com/dotnet/csharplang/blob/master/proposals/patterns.md
static string M(Person person)
{
return person switch
{
Professor (_, var ln, var s) =>
$"Dr. {ln}, Professor of {s}",
Student (var fn, _, var (_, ln, _)) =>
$"{fn}, Student of Dr. {ln}",
{ LastName: "Campbell", FirstName: var fn } =>
$"Please, enroll, {fn}",
_ =>
"Come back next year!"
};
}

25. https://github.com/dotnet/csharplang/blob/master/proposals/async-streams.md#iasyncdisposable
public interface IAsyncDisposable
{
Task DisposeAsync();
}

26. https://github.com/dotnet/csharplang/blob/master/proposals/async-streams.md#iasyncenumerable--iasyncenumerator
public interface IAsyncEnumerable<out T>
{
IAsyncEnumerator<T> GetAsyncEnumerator();
}
public interface IAsyncEnumerator<out T>
{
Task<bool> WaitForNextAsync();
T TryGetNext(out bool success);
}

27. interface ILogger
{
void Log(LogLevel level, string message);
}
class ConsoleLogger : ILogger
{
// send message
public void Log(LogLevel level, string message) { }
}
https://github.com/dotnet/csharplang/blob/master/proposals/default-interface-methods.md
interface ILogger
{
void Log(LogLevel level, string message);
void Log(Exception ex) => Log(LogLevel.Error, ex.ToString());
}
class ConsoleLogger : ILogger
{
// send message
public void Log(LogLevel level, string message) { }
}

28. https://github.com/dotnet/csharplang/blob/master/proposals/default-interface-methods.md
interface ILogger
{
void Log(LogLevel level, string message);
void Log(Exception ex) => Log(LogLevel.Error, ex.ToString());
}
class TelemetryLogger : ILogger
{
// send message
public void Log(LogLevel level, string message) { }
// capture crash dump and send message
public void Log(Exception ex) { }
}

29. class Person(string First, string Last);
class Person : IEquatable<Person>
{
public string First { get; }
public string Last { get; }
public Person(string First, string Last) => (this.First, this.Last) = (First, Last);
public void Deconstruct(out string First, out string Last) => (First, Last) = (this.First, this.Last);
public bool Equals(Person other) => other != null && First == other.First && Last == other.Last;
public override bool Equals(object obj) => obj is Person other ? Equals(other) : false;
public override int GetHashCode() => GreatHashFunction(First, Last);
…
}

30. https://docs.microsoft.com/en-us/dotnet/csharp/
https://docs.microsoft.com/en-us/dotnet/csharp/whats-new/
https://github.com/dotnet/roslyn/blob/master/docs/Language%20Feature%20Status.md
https://github.com/dotnet/csharplang/
https://github.com/dotnet/roslyn

31. https://github.com/dotnet/csharplang/wiki
https://github.com/dotnet/csharplang/wiki/vNext-Preview
https://github.com/dotnet/csharplang/wiki/Nullable-Reference-Types-Preview

32. https://channel9.msdn.com/events/Build/2018/BRK2155
https://channel9.msdn.com/Events/dotnetConf/2018/S103

33. https://visualstudio.microsoft.com/vs/
https://code.visualstudio.com/
http://www.linqpad.net/
https://roslynpad.net/
https://sharplab.io/

34. https://github.com/paulomorgado/TugaIT-2018-Demos
https://github.com/paulomorgado/TugaIT-2018-FutureDemos-Nullable
https://github.com/paulomorgado/TugaIT-2018-FutureDemos-Goodies

35. @farfetch https://www.farfetch.com/

38. * Para quem não puder preencher durante a reunião,
iremos enviar um email com o link à tarde

39. 15/09/2018 – Lisboa
24/11/2018 – Lisboa
Reserva estes dias na agenda! :)