patternmatching.cs

public static void SwitchPattern(object o)
{
    switch (o)
    {
        case null:
            Console.WriteLine("it's a constant pattern");
            break;
        case int i:
            Console.WriteLine("it's an int");
            break;
        case Person p when p.FirstName.StartsWith("Ka"):
            Console.WriteLine($"a Ka person {p.FirstName}");
            break;
        case Person p:
            Console.WriteLine($"any other person {p.FirstName}");
            break;
        case var x:
            Console.WriteLine($"it's a var pattern with the type {x?.GetType().Name} ");
            break;
        default:
            break;
    }
}

class Geometry();
class Triangle(int Width, int Height, int Base) : Geometry;
class Rectangle(int Width, int Height) : Geometry;
class Square(int width) : Geometry;
 
Geometry g = new Square(5);
switch (g)
{
    case Triangle(int Width, int Height, int Base):
        WriteLine($"{Width} {Height} {Base}");
        break;
    case Rectangle(int Width, int Height):
        WriteLine($"{Width} {Height}");
        break;
    case Square(int Width):
        WriteLine($"{Width}");
        break;
    default:
        WriteLine("<other>");
        break;
}