Category: Design Patterns

<p><code style="display:block;white-space:pre-wrap">
using System;

namespace SingletonPatternEx
{
    public sealed class Singleton
    {
        private static readonly Singleton instance=new Singleton();
        private int numberOfInstances = 0;
        //Private constructor is used to prevent
        //creation of instances with 'new' keyword outside this class
        private Singleton()
        {
         Console.WriteLine("Instantiating inside the private constructor.");
         numberOfInstances++;
         Console.WriteLine("Number of instances ={0}", numberOfInstances);
        }
        public static Singleton Instance
        {
            get
            {
                Console.WriteLine("We already have an instance now.Use it.");
               return instance;
            }
        }
    }
    class Program
    {
        static void Main(string[] args)                                                                                              
        {
            Console.WriteLine("***Singleton Pattern Demo***\n");
            //Console.WriteLine(Singleton.MyInt);
            // Private Constructor.So,we cannot use 'new' keyword.            
            Console.WriteLine("Trying to create instance s1.");
            Singleton s1 = Singleton.Instance;
            Console.WriteLine("Trying to create instance s2.");
            Singleton s2 = Singleton.Instance;
            if (s1 == s2)
            {
                Console.WriteLine("Only one instance exists.");
            }
            else
            {
                Console.WriteLine("Different instances exist.");
            }
            Console.Read();
        }
    }
}
</code></p>

<p><code style="display:block;white-space:pre-wrap">
//BasicCar.cs
using System;

namespace PrototypePattern
{
   public abstract class BasicCar
    {
        public string ModelName{get;set;}
        public int Price {get; set;}
        public static int SetPrice()
        {
            int price = 0;
            Random r = new Random();
            int p = r.Next(200000, 500000);
            price = p;
            return price;
        }
        public abstract BasicCar Clone();
    }
}
//Nano.cs
using System;

namespace PrototypePattern
{
    public class Nano:BasicCar
    {
        public Nano(string m)
        {
            ModelName = m;
        }

        public override BasicCar Clone()
        {
            return (Nano) this.MemberwiseClone();//shallow Clone
        }
    }
}
//Ford.cs

using System;

namespace PrototypePattern
{
    public class Ford:BasicCar
    {
        public Ford(string m)
        {
            ModelName = m;
        }

        public override BasicCar Clone()
        {
            return (Ford)this.MemberwiseClone();
        }
    }
}

//Client

using System;

namespace PrototypePattern
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine("***Prototype Pattern Demo***\n");
            //Base or Original Copy
            BasicCar nano_base = new Nano("Green Nano") {Price = 100000};
            BasicCar ford_base = new Ford("Ford Yellow") {Price = 500000};
            BasicCar bc1;
            //Nano
            bc1 = nano_base.Clone();
            bc1.Price = nano_base.Price+BasicCar.SetPrice();
            Console.WriteLine("Car is: {0}, and it's price is Rs. {1} ",bc1.ModelName,bc1.Price);

            //Ford            
            bc1 = ford_base.Clone();
            bc1.Price = ford_base.Price+BasicCar.SetPrice();
            Console.WriteLine("Car is: {0}, and it's price is Rs. {1}", bc1.ModelName, bc1.Price);

            Console.ReadLine();
        }
    }
}
</code></p>