Dependency Injection in C#

             Dependency Injection is a Software Design Pattern for make Loosely coupled code.There are 3 main ways to implement dependency injection.They are

1. Constructor Injection
2. Property Injection
3. Method Injection

1.Constructor Injection

                            It uses only one Parameterized constructor.

(e.g)

1.

using System;

interface ICar

{

void ShowColor();

}

class Maruthi:ICar

{

public void ShowColor()

{

Console.WriteLine("Maruthi Car");

}

}

class ConstructorInjection

{

   private Maruthi _maruthi;

public ConstructorInjection(Maruthi m)

{

_maruthi=m;

}

public void ShowColor()

{

_maruthi.ShowColor();

}

}

public class Program

{

public static void Main()

{

ConstructorInjection cn = new ConstructorInjection(new Maruthi());

cn.ShowColor();

}

}

2.

public class UserLogic
{
    private GoogleOAuthService _authService;
    private IEmailService _emailService;

    public UserLogic(IEmailSevice emailService)
    {
        _authService = new GoogleOAuthService();
        _emailService = emailService;
    }
    ...
}

...
    GoogleEmailService googleEmailService = new GoogleEmailService();
    UserLogic userLogic = new UserLogic(googleEmailService);
...

      

Output

Maruthi Car

2.Property Injection  
                                   
(e.g)
public class UserLogic
{
    private GoogleOAuthService _authService;
    private IEmailService _emailService;

    public IEmailService EmailService
    {
        get
        {
            return _emailService;
        }
        set
        {
            _emailService = value;
        }
    }

    public UserLogic()
    {
        _authService = new GoogleOAuthService();
    }
    ...

}


...
    OutlookEmailService outlookEmailService = new OutlookEmailService();
    UserLogic userLogic = new UserLogic()
        {
            EmailService = outlookEmailService
        };
...

           

3.Method Injection  

(e.g)
public class UserLogic
{
    private GoogleOAuthService _authService;

    public UserLogic()
    {
        _authService = new GoogleOAuthService();
        _emailService = new OutlookEmailService() // or Google;
    }

    public void Register(string emailAddress, string password, IEmailService emailService)
    {
        var authResult = _authService.RegisterUser(emailAddress,password);
        emailService.SendMail(emailAddress, authResult.ConfirmationMessage);
    }
}

...
    OutlookEmailService outlookEmailService = new OutlookEmailService();
    UserLogic userLogic = new UserLogic();
    userLogic.Register(email, password, outlookEmailService);
...