Proxy Design Pattern

Examples/Jalilpour/DeliveryFactory.cs

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+
+namespace Examples.Jalilpour
+{
+    public enum CargoType
+    {
+        Air,
+        Ship,
+        Train
+    }
+
+    public class DeliveryService
+    {
+        public Delivery Create(CargoType cargoType)
+        {
+            if (cargoType == CargoType.Air)
+            {
+                return new AirDeliveryFactory().CreateDelivery();
+            }
+            else if (cargoType == CargoType.Ship)
+            {
+                return new ShipDeliveryFactory().CreateDelivery();
+            }
+            else if (cargoType == CargoType.Train)
+            {
+                return new TrainDeliveryFactory().CreateDelivery();
+            }
+            throw new InvalidOperationException();
+        }
+    }
+
+    public abstract class Delivery
+    {
+        public abstract void DeliverCargo();
+    }
+
+    public class AirDelivery : Delivery
+    {
+        public override void DeliverCargo()
+        {
+            throw new NotImplementedException();
+        }
+    }
+
+    public class TrainDelivery : Delivery
+    {
+        public override void DeliverCargo()
+        {
+            throw new NotImplementedException();
+        }
+    }
+
+    public class ShipDelivery : Delivery
+    {
+        public ShipDelivery()
+        {
+
+        }
+        public ShipDelivery(string origin, string destination)
+        {
+
+        }
+        public override void DeliverCargo()
+        {
+            throw new NotImplementedException();
+        }
+    }
+
+
+
+    public abstract class DeliveryFactory
+    {
+        public abstract Delivery CreateDelivery();
+    }
+
+    public class AirDeliveryFactory : DeliveryFactory
+    {
+        private static AirDelivery airDelivery;
+        public override Delivery CreateDelivery()
+        {
+            if (airDelivery == null)
+                airDelivery = new AirDelivery();
+            return airDelivery;
+        }
+    }
+
+    public class ShipDeliveryFactory : DeliveryFactory
+    {
+        public override Delivery CreateDelivery()
+        {
+            return new ShipDelivery("BandarAbbas", "Astarakhan");
+        }
+    }
+
+    public class TrainDeliveryFactory : DeliveryFactory
+    {
+        private static bool hasAlreadyInstance;
+        public override Delivery CreateDelivery()
+        {
+            if (hasAlreadyInstance)
+            {
+                init();
+                return new TrainDelivery();
+            }
+            else
+            {
+                hasAlreadyInstance = true;
+                return new TrainDelivery();
+            }
+        }
+        private void init()
+        {
+            throw new NotImplementedException();
+        }
+    }
+
+
+
+    /// <summary>
+    /// Imagine it is a library and we make it as a package. so users or customers,
+    /// can't change your code, but they want to add a new behavior like Truck. so, how you can solve it.
+    /// </summary>
+    public class Truck : Delivery
+    {
+        public override void DeliverCargo()
+        {
+            Console.WriteLine("Delivering...");
+        }
+    }
+    public static class DeliveryFactoryExtentionMethod
+    {
+        public static void DeliverCargoByTruck(this Delivery truck)
+        {
+            throw new NotImplementedException();
+        }
+    }
+    ///
+
+
+    public class Program()
+    {
+        public void main()
+        {
+            Truck truck = new();
+            truck.DeliverCargoByTruck();
+        }
+    }
+}

Payment/Ecommerce.cs

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+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Security.Cryptography;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace Payment
+{
+    public enum PaymetType
+    {
+        CreditCard,
+        PayPal,
+        CryptoCurrency
+    }
+    public class Ecommerce
+    {
+        public void Pay(PaymetType paymetType, decimal amount)
+        {
+            switch (paymetType)
+            {
+                case PaymetType.CreditCard:
+                    new CreditCardProcessor().Pay(amount);
+                    break;
+                case PaymetType.PayPal:
+                    new PayPalProcessor().Pay(amount);
+                    break;
+                case PaymetType.CryptoCurrency:
+                    new CryptoAdapter(new CryptoCurrencyProcessor()).Pay(amount);
+                    break;
+                default: throw new Exception("NullPaymentProcessor");
+            }
+        }
+
+
+        interface IPaymentProcessor
+        {
+            public void Pay(decimal amount);
+        }
+
+        public class CreditCardProcessor : IPaymentProcessor
+        {
+            public void Pay(decimal amonut)
+            {
+                Console.WriteLine(amonut + (2 * amonut / 100));
+            }
+        }
+
+        public class PayPalProcessor : IPaymentProcessor
+        {
+            public void Pay(decimal amonut)
+            {
+                throw new NotImplementedException();
+            }
+        }
+
+
+        // Supppose this class comes from a third party library
+        #region CryptoCurrencyProcessor
+        public interface ICryptoCurrencyProcessor
+        {
+            public bool PayByCrypto(decimal amount);
+        }
+        public class CryptoCurrencyProcessor : ICryptoCurrencyProcessor
+        {
+            public bool PayByCrypto(decimal amonut)
+            {
+                throw new NotImplementedException();
+            }
+        }
+        #endregion
+
+
+        // The CryptoAdapter makes the CryptoCurrencyProcessor compatible with the PaymentProcessor interface
+        class CryptoAdapter : IPaymentProcessor
+        {
+            private readonly CryptoCurrencyProcessor _cryptoCurrencyProcessor;
+
+            public CryptoAdapter(CryptoCurrencyProcessor cryptoCurrencyProcessor)
+            {
+                _cryptoCurrencyProcessor = cryptoCurrencyProcessor;
+            }
+
+            public void Pay(decimal amonut)
+            {
+                _cryptoCurrencyProcessor.PayByCrypto(amonut);
+            }
+        }
+
+    }
+}