ASP.NET-MVC – Why does 2 constructor in Default AccountController provided by MVC?

public class AccountController: Controller
{
 public IFormsAuthentication FormsAuth {get; private set; }
 public IMembershipService MembershipService {get; private set; }

 public AccountController()
: this(null, null)< br /> {
 }
 public AccountController(IFormsAuthentication formsAuth, IMembershipService membershipService)
 {
 FormsAuth = formsAuth ?? new FormsAuthenticationService();
 MembershipService = membershipService ?? new AccountMembershipService();

 //---
 }

public AccountController(IFormsAuthentication formsAuth, 
 IMembershipService membershipService)
 {
 FormsAuth = formsAuth ?? new FormsAuthenticationService();
 MembershipService = membershipService ?? new AccountMembershipService();
 }

public AccountController()
: this(null, null)
 {
 }

This is the framework The generated default AccountController.cs.

public class AccountController: Controller
{
 public IFormsAuthentication FormsAuth {get; private set; }
 public IMembershipService MembershipService {get; private set; }

 public AccountController()
: this(null, null)
 {
 }
 public AccountController(IFormsAuthentication formsAuth, IMembershipService membershipService)
 {
 FormsAu th = formsAuth ?? new FormsAuthenticationService();
 MembershipService = membershipService ?? new AccountMembershipService();

 //---
 }

This It is easy to understand.

public AccountController(IFormsAuthentication formsAuth, 
 IMembershipService membershipService)
 {
 FormsAuth = formsAuth ?? new FormsAuthenticationService(); 
 MembershipService = membershipService ?? new AccountMembershipService();
 }

What is this? What is its purpose? Is it specific to the account controller or a requirement of other controllers? And, why should I include it in my project?

public AccountController()
: this(null, null)
 {
 }

They seem to be in other This type of constructor is used in two places.

Thank you for your help

This is actually the implementation of the Bastard Injection anti-pattern .

Our idea is to support constructor injection to allow dependency injection (DI) while still providing a default constructor for default behavior.

There is actually no need to use the default Constructor, but if you omit it, you must provide a custom IControllerFactory, because DefaultControllerFactory assumes that all controllers have a default constructor.

ASP.NET MVC considered DI when it was built, but I want to keep it Simple, Bastard Injection mode is used for project templates to avoid forcing developers to use a specific IControllerFactory.