How to use Pattern Matching in C#

using System;
class PatternMatching
{
  // Defining structs
  public struct Rectangle
  {
      public double Length { get; set;}
      public double Height { get; set;}
      public Rectangle(double l, double h)
      {
          Length = l;
          Height = h;
      }
  }
  public struct Circle
  {
      public double Radius { get; set;}
      public Circle(double r)
      {
          Radius = r;
      }
  }
  // Defining functions with parameter type object
  static public double getArea(object Shape)
  {
    // Pattern matching in If Statements
    // Variables also declared after casting in If Statement
    if (Shape is Circle c){
      return 3.142 * c.Radius * c.Radius;
    }
    else if(Shape is Rectangle r){
      return r.Length * r.Height;
    }
    return 0;
  }
  static public double getPerimeter(object Shape)
  {
    // Pattern matching in If Statements
    // Variables also declared after casting in If Statement
    if (Shape is Circle c){
      return 2 * 3.142 * c.Radius;
    }
    else if(Shape is Rectangle r){
      return r.Length * 2 + r.Height * 2;
    }
    return 0;
  }
  static void Main()
  {
    // Declaring variables
    Circle c = new Circle();
    c.Radius = 5;
    Rectangle r = new Rectangle();
    r.Height = 3;
    r.Length = 4;
    
    // The same function is called for both variables
    System.Console.WriteLine(getArea(r));
    System.Console.WriteLine(getArea(c));
    System.Console.WriteLine(getPerimeter(r));
    System.Console.WriteLine(getPerimeter(c));
  }
}

using System;
class PatternMatching
{
  // Defining structs
  public struct Rectangle
  {
      public double Length { get; set;}
      public double Height { get; set;}
      public Rectangle(double l, double h)
      {
          Length = l;
          Height = h;
      }
  }
  public struct Circle
  {
      public double Radius { get; set;}
      public Circle(double r)
      {
          Radius = r;
      }
  }
  // Defining functions with parameter type object
  static public double getArea(object Shape)
  {
    // Pattern matching in Switch Case Statements
    // Variables also declared after casting in Case Statement
    switch (Shape){
      case Rectangle r:
        return r.Length * r.Height;
      case Circle c:
        return 3.142 * c.Radius * c.Radius;
    }
    return 0;
  }
  static public double getPerimeter(object Shape)
  {
    // Pattern matching in Switch Case Statements
    // Variables also declared after casting in Case Statement
    switch (Shape){
      case Rectangle r:
        return r.Length * 2 + r.Height * 2;
      case Circle c:
        return 2 * 3.142 * c.Radius;
    }
    return 0;
  }
  static void Main()
  {
    // Declaring variables
    Circle c = new Circle();
    c.Radius = 5;
    Rectangle r = new Rectangle();
    r.Height = 3;
    r.Length = 4;
    // The same function is called for both variables
    System.Console.WriteLine(getArea(r));
    System.Console.WriteLine(getArea(c));
    System.Console.WriteLine(getPerimeter(r));
    System.Console.WriteLine(getPerimeter(c));
  }
}