Assignment with switch and pattern matching #csharp

README.md

Switch expressions

• https://developers.redhat.com/blog/2020/02/27/c-8-pattern-matching/
• https://drakelambert.dev/2019/12/C%23-8-Switch-Expressions-with-Pattern-Matching.html

SwitchExpression.cs

// By value
public enum Directions { Up, Down, Right, Left }
public enum Orientation { North, South, East, West }

Orientation orientation = direction switch
{
  Directions.Up    => Orientation.North,
  Directions.Right => Orientation.East,
  Directions.Down  => Orientation.South,
  Directions.Left  => Orientation.West,
};

// Tuple value
public static string RockPaperScissors(string first, string second)
    => (first, second) switch
    {
        ("rock", "paper") => "rock is covered by paper. Paper wins.",
        ("rock", "scissors") => "rock breaks scissors. Rock wins.",
        ("paper", "rock") => "paper covers rock. Paper wins.",
        ("paper", "scissors") => "paper is cut by scissors. Scissors wins.",
        ("scissors", "rock") => "scissors is broken by rock. Rock wins.",
        ("scissors", "paper") => "scissors cuts paper. Scissors wins.",
        (_, _) => "tie"
    };

static Sector GetSector(Point point)  => point switch
{
    (0, 0) => Sector.Origin,
    (2, _) => Sector.One,
    var (x, y) when x > 0 && y > 0 => Sector.Two,
    (1, var y) when y < 0 => Sector.Three,
    _ => Sector.Unknown
};

// Complicated pattern
var x = strangeObject switch
{
  var n when n is Square s && s.Side > 20 => 10,
  var n when n is Circle c && c.Radius < 10 => 50,
  _ => 0
};

var percent2 = price switch
{
  var n when n >= 1000000 => 7f,
  var n when n < 1000000 && n >= 900000 => 7.1f,
  var n when n < 900000 && n >= 800000 => 7.2f,
  _ => 0f // default value
};

// Deconstructable
public class Point
{
    public int X { get; }
    public int Y { get; }

    public Point(int x, int y) => (X, Y) = (x, y);

    public void Deconstruct(out int x, out int y) => (x, y) = (X, Y);
}

public enum Quadrant
{
    Unknown,
    Origin,
    One,
    Two,
    Three,
    Four,
    OnBorder
}

static Quadrant GetQuadrant(Point point) => point switch
{
    (0, 0) => Quadrant.Origin,
    var (x, y) when x > 0 && y > 0 => Quadrant.One,
    var (x, y) when x < 0 && y > 0 => Quadrant.Two,
    var (x, y) when x < 0 && y < 0 => Quadrant.Three,
    var (x, y) when x > 0 && y < 0 => Quadrant.Four,
    var (_, _) => Quadrant.OnBorder,
    _ => Quadrant.Unknown
};

// Property pattern
object o = null;

var x = o switch
{
  Car { Wheels: 3 } c => 6
};