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.