PaymentStrategyFactory.cs

public static class PaymentStrategyFactory
{
    public static IPaymentStrategy Create(string paymentProvider)
    {
        switch (paymentProvider)
        {
            case "Paypal": return new PaypalPaymentStrategy();
            case "ApplePay": return new ApplePayPaymentStrategy();
            default: return NullPaymentStrategy.Instance;
        }
    }
}