Factory Method sample code

BlackcatV2.cs

public class Blackcat_V2 : IShipper
{
    private double _discount;

    private Blackcat_V2()
    {
    }

    public static IShipper CreateBlackcatV2(double discount)
    {
        var blackcatV2 = new Blackcat_V2();
        blackcatV2.SetDiscount(discount);

        return blackcatV2;
    }

    private void SetDiscount(double discount)
    {
        this._discount = discount;
    }


    public double CalculateFee()
    {
        return 100 * this._discount;
    }
}

public interface IShipper
{
    double CalculateFee();
}