Design Patterns - Strategy Pattern

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Threading.Tasks;

namespace DesignPattern_StrategyPattern

{

   class Program

   {

      static void Main(string[] args)

      {

         /* STRATEGY PATTERN (POLICY PATTERN):

          * Strategy lets the algorithm vary independently 
          * from clients that use it.

          * When the program is running, we can switch between different 
          * type of algorithms

          * For instance, a class that performs validation on incoming data

          * may use a strategy pattern to select a validation 
          * algorithm based on the type of data, 
          * the source of the data, user choice,

          * or other discriminating factors. These factors are not known 
          * for each case until run-time, and may require 
          * radically different validation to be performed.

          */

          ICalculate calculate = null;

          while (true)

          {

             try

             {

                Console.WriteLine("Choose an operation! ( 1 = Plusus, 2 = Minus )");

                StrategyType strategyType = (StrategyType)Convert.ToInt32(Console.ReadLine());

                Console.WriteLine("Enter the first number");

                int value1 = Convert.ToInt32(Console.ReadLine());

                Console.WriteLine("Enter the second number");

                int value2 = Convert.ToInt32(Console.ReadLine());

                switch (strategyType)

                {

                   case StrategyType.Plussus:

                      calculate = new Plussus();

                      Console.WriteLine("Operation: Plusus, Result: " + calculate.Calculate(value1, value2));

                      break;

                   case StrategyType.Minus:

                      calculate = new Minus();

                      Console.WriteLine("Operation: Minus, Result: " + calculate.Calculate(value1, value2));

                      break;

                }

             }

             catch (Exception)

             {

                Console.WriteLine("Enter a valid number!");

             }

         }

      }

   }

}

*********************

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Threading.Tasks;

namespace DesignPattern_StrategyPattern

{

   //The interface for the strategies

   public interface ICalculate

   {

      //Method is defined in the interface

      int Calculate(int value1, int value2);

   }

}

*********************

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Threading.Tasks;

namespace DesignPattern_StrategyPattern

{

   //Strategy: Minus

   public class Minus : ICalculate

   {

      public int Calculate(int value1, int value2)

      {

         //The minus logis is defined

         return value1 - value2;

      }

   }

}

*********************

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Threading.Tasks;

namespace DesignPattern_StrategyPattern

{

   //Strategy: Plussus

   public class Plussus:ICalculate

   {

      public int Calculate(int value1, int value2)

      {

         //The plussus logic is defined

         return value1 + value2;

      }

   }

}

*********************

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Threading.Tasks;

namespace DesignPattern_StrategyPattern

{

   enum StrategyType

   {

      Plussus = 1,

      Minus = 2

   }

}

*********************

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Threading.Tasks;

namespace DesignPattern_StrategyPattern

{

   //The client

   public class CalculateClient

   {

      private ICalculate calculate;

      public CalculateClient(ICalculate strategy)

      {

         this.calculate = strategy;

      }

      public int Calculate(int value1, int value2)

      {

         return calculate.Calculate(value1, value2);

      }

   }

}