Does Upcasting and Downcasting in C# Qualify as Polymorphism?

In the example below, I perform both upcasting and downcasting to represent an object as different types at runtime. I understand that polymorphism typically involves treating an object as an instance of its parent class and using overridden virtual methods for dynamic behavior. However, I’m unsure if the act of casting itself—switching an object’s type through upcasting or downcasting—falls under polymorphism, or if polymorphism only refers to runtime behavior changes in overridden methods.

Specifically, does polymorphism strictly relate to virtual or overloaded methods that change behavior at runtime, or can it also be interpreted as converting objects to different types and treating them accordingly?

CSHARPCopied
namespace Inheritance
{
    internal class Program
    {
        static void Main(string[] args)
        {
            Vehicle supersport = new SupersportCar("BMW", "m5", 1730, 3_000_000, 507, 520, 4.7);
            SupersportCar ssc = (SupersportCar)new Vehicle("BMW", "m5", 1730, 3_000_000);
        }
    }

    class Vehicle
    {
        public string Brand { get; set; }
        public string Model { get; set; }
        public int Weight { get; set; }
        public double Price { get; set; }

        public Vehicle(string Brand, string Model, int Weight, double Price)
        {
            this.Brand = Brand;
            this.Model = Model;
            this.Weight = Weight;
            this.Price = Price;

            Console.WriteLine("YENİ ARAÇ");
            Console.WriteLine("Vehicle Constructer");
            Console.WriteLine($"""
            Araç Markası: {Brand}
            Araç modeli: {Model}
            Araç ağırlığı: {Weight}
            Araç fiyatı: {Price}
            """);
            Console.WriteLine("*********\n");
        }

        public static void StaticArac()
        {

        }
    }

    class Car : Vehicle
    {
        public double Power { get; set; }
        public double Torque { get; set; }

        public Car(string Brand, string Model, int Weight, double Price, double Power, double Torque) : base(Brand,Model,Weight,Price)
        {
            this.Power = Power;
            this.Torque = Torque;

            Console.WriteLine("YENİ ARAÇ");
            Console.WriteLine("Car Constructer");
            Console.WriteLine($"""
            Araç Markası: {Brand}
            Araç modeli: {Model}
            Araç ağırlığı: {Weight}
            Araç fiyatı: {Price}
            Araç gücü: {Power} hp
            Araç torku: {Torque} NM
            """);
            Console.WriteLine("*********\n");
        }
    }

    class SupersportCar : Car
    {
        public double FromZeroToHundered { get; set; }

        public SupersportCar(string Brand, string Model, int Weight, double Price, double Power, double Torque, double FromZeroToHundered) : base(Brand, Model, Weight, Price, Power, Torque)
        {
            this.FromZeroToHundered = FromZeroToHundered;

            Console.WriteLine("YENİ ARAÇ");
            Console.WriteLine("SupersportCar Constructer");
            Console.WriteLine($"""
            Araç Markası: {Brand}
            Araç modeli: {Model}
            Araç ağırlığı: {Weight}
            Araç fiyatı: {Price}
            Araç gücü: {Power} hp
            Araç torku: {Torque} NM
            0-100 hızlanması: {FromZeroToHundered} sn
            """);
            Console.WriteLine("*********");
        }
    }

}