Strategy Design Pattern Using C# Sample

Introduction

 

Strategic design pattern is a behavioral design pattern in which the behavior of the object is encapsulated with a common function name.

 

Where to use Strategic design pattern?

 

When different customers have a common strategy (common operation name) but a different action to perform, then we can use strategic design pattern.

 

Why use Strategic design pattern?

 

As we discussed previously, customers have a common operation name to perform, so that we can share  a common interface to all customers to perform their actions as per their need.

 

Players in this pattern,

• Strategy: It defines contract with common operation.
• ConcreteStrategy : It implements contact defined by Strategy.
• Product: It fullfils customer requirements using ConcreteStrategy objects by referring Strategy contract.

We will see strategic design pattern with an example. 

Problem definition

 

Define a common operation for students to access different actions like addition, subtraction, multiplication, division.

 

Players in this case,

• Strategy : IOperator
• ConcreteStrategy: AddOperator, SubtractOperator, MultiplyOperator, DivisionOperator.
• Product : Calculator

Below is the IOperator contract which defined common operation called ExecuteOperation

namespace Strategy.Design.Pattern.Contract
{
    public interface IOperator
    {
        void ExecuteOperation(int a, int b);
    }
}

Below are the concrete operators which implement contract defined by IOperator

using Strategy.Design.Pattern.Contract;
using static System.Console;

namespace Strategy.Design.Pattern.Business
{
    public class AddOperator : IOperator
    {
        public void ExecuteOperation(int a, int b)
        {
            WriteLine($"{nameof(AddOperator)} result: {a + b}");
        }
    }
}

using Strategy.Design.Pattern.Contract;
using static System.Console;

namespace Strategy.Design.Pattern.Business
{
    public class SubtractOperator : IOperator
    {
        public void ExecuteOperation(int a, int b)
        {
            WriteLine($"{nameof(SubtractOperator)} result: {a - b}");
        }
    }
}

using Strategy.Design.Pattern.Contract;
using static System.Console;

namespace Strategy.Design.Pattern.Business
{
    public class MultiplyOperator : IOperator
    {
        public void ExecuteOperation(int a, int b)
        {
            WriteLine($"{nameof(MultiplyOperator)} result: {a * b}");
        }
    }
}

using Strategy.Design.Pattern.Contract;
using static System.Console;

namespace Strategy.Design.Pattern.Business
{
    public class DivisionOperator : IOperator
    {
        public void ExecuteOperation(int a, int b)
        {
            WriteLine($"{nameof(DivisionOperator)} result: {a / b}");
        }
    }
}

Below is the our product calculator which is going to be used by customers with the help of IOperator contract

using Strategy.Design.Pattern.Contract;

namespace Strategy.Design.Pattern.Business
{
    public class Calculator
    {
        private IOperator _operator;

        public Calculator(IOperator ioperator)
        {
            _operator = ioperator;
        }

        public void Calculate(int a, int b)
        {
            _operator.ExecuteOperation(a, b);
        }
    }
}

Below is the Student class in which Student uses a calculator to fullfil his/her requirement.

using Strategy.Design.Pattern.Business;
using static System.Console;

namespace Strategy.Design.Pattern
{
    class Student
    {
        static void Main(string[] args)
        {
            Calculator oprt = new Calculator(new AddOperator());
            oprt.Calculate(20, 10);

            oprt = new Calculator(new SubtractOperator());
            oprt.Calculate(20, 10);

            oprt = new Calculator(new MultiplyOperator());
            oprt.Calculate(20, 10);

            oprt = new Calculator(new DivisionOperator());
            oprt.Calculate(20, 10);

            ReadLine();
        }
    }
}

Below is the snap of the output window of the above code:

 

 

Summary

 

In this article we understood about what strategic design pattern is and how to use it.