C Sharp

C# 8.0 and .Net Core 3.0

Intro

Here is the history of C#

• 2.0 included generics
• 3.0 Added Linq with Lambda and anonymous types
• 4.0 Added Dynamics
• 5.0 Added Async and Await
• 6.0 Added Null propagating operator (targer?.IsActive ?? false;
• 7.0 Expressions and Tuples

C# 8.0 brings

• Nullable Reference Types
• Pattern Matching
• Indices and Ranges
• Built-in Json Support
• Windows Desktop Support
• Build and Deploy Improvements
• Other Language Improvements
• Other .NET Core Platform Improvements

Nullable Reference Types

This allows you to specify a possibility of null. e.g.

class
{
    public string? Title {get; set;}
    public List<Comment> Title {get;} = new List<Comment>();
}

Bad code is highlighted a compile time with CS8618 Non-nullable property and via intellisence.

You and enable and restore this feature on a file basis using #nullable enable and #nullable restore

Pattern Matching

Deconstructors

Hardcoded unlike javascript

claas Test
{
    public PropA {get; set;}
    public PropB {get; set;}
    public PropC {get; set;}
    public PropD {get; set;}

    Test(string a, string b, string c, string d)
    {
      PropA = a;
      PropB = b;
      PropC = c;
      PropD = d;
    }

    void Deconstructor(
       out string a,
       out string b,
       out string c,
       out string d)
    {
       a = PropA;
       b = PropB
       c = PropC;
       d = PropD;
    } 
}

Positional Pattern

public static bool TestHasCValue5(Test inTest)
{
    return inTest is Test(_,_,"5",_);
}

Property Pattern

public class Employee
{
    public string FirstName {get; set;}
    public string LastName {get; set;}
    public string Region {get; set;}
    public Employee ReportsTo {get; set;}
}
public static bool IsUsBasedWithUkManager(object o)
{
    return o is Employee e && 
        e is { Region: "US", ReportsTo: {Region:" UK" }};
}

Tuple Pattern

public statis bool MakesBlue(Color c1, Color c2)
{
    return (c1,c2) is (Color.Red, Color.Green) ||
           (c2,c1) is (Color.Red, Color.Green);
}