Single Responsibility Principle

A class or module should have only one reason to change. This means that a class should have only one responsibility or job to do, and all its methods should be related to that job. This makes the code easier to understand, modify, and test.

Benefits:

• Code will be easier to understand
• Better maintainability
• Testability
• Parallel Development
• Reusability

How to implement SRP
Project Requirement:

• The application should be able to Add and Delete employee
• With every add and delete one email should be sent
• In case of exception, a text log file will be generated

Solution 1: Without SRP Principles
We can send an email and create a log of both Add & Delete methods separately. But if any issues arise we have to solve both methods which is not a good practice.

public class Employee
    {
        public void Add()
        {
            try
            {
                Console.WriteLine("Add Employee");
                // Then write code for sending email
            }
            catch (Exception ex)
            {
                Console.WriteLine(ex.ToString());
            }
        }

        public void Delete()
        {
            try
            {
                Console.WriteLine("Delete Employee");
                // Then write code for sending email
            }
            catch (Exception ex) 
            {
                Console.WriteLine(ex.ToString()); 
            }
        }
    }

Solution 2: Using SRP Principles

• So we create Ilogger and IMailer interfaces and implement these interfaces with two classes.
• Mailer class takes responsibility for sending email
• The logger class takes responsibility for creating the log

Instance create from employee constructor and then calling email-sender & logger method using those instance

public interface IMailer
 {
    void SendEmail();
 }

 public class Mailer : IMailer
    {
        public void SendEmail()
        {
            //write code for sending email.
        }
    }

 public interface ILogger
    {
        void LogException();
    }
    public class Logger : ILogger
    {
        public void LogException()
        {
            //write code for saving log exceptions.
        }
    }

interface IEmployee
    {
        void Add();
        void Delete();
    }
    public class Employee: IEmployee
    {
        ILogger _logger;
        IMailer _mailer;
        public Employee()
        {
            _logger = new Logger();
            _mailer = new Mailer();
        }   
        public void Add()
        {
            try
            {
                Console.WriteLine("Add Employee");
                _mailer.SendEmail();
            }
            catch (Exception ex)
            {
                _logger.LogException();
            }
        }
        public void Delete()
        {
            try
            {
                Console.WriteLine("Add Employee");
                _mailer.SendEmail();
            }
            catch (Exception ex)
            {
                _logger.LogException();
            }
        }
    }