Dependency Injection - When to use property injection

Question

I\'ve a class which have a constructor like this:

    private string _someString;
    private ObjectA _objectA;
    private ObjectB _objectB;
    private Diction         


        

Answer 1

You should use property injection (or setter injection) when object creation of your type is out of your control. Like aspx Page, HttpHandler, ApiController etc. For all others situations it is recommended to use constructor injection.

To resolve dependencies for aspx Page using StructureMap, i use the following approach.

First, I create a BasePage class and use StructureMap's BuildUp() method in the constructor to resolve dependencies of the derived pages. Code is given below:

public class BasePage : Page
{
    public BasePage()
    {
        // instruct StructureMap to resolve dependencies
        ObjectFactory.BuildUp(this);
    }
}

public class Default : BasePage
{
     public ICustomerService customerService { get; set; }

     protected void Page_Load(object sender, EventArgs e)
     {
         // can start using customerService
     }
}

public class Login : BasePage
{
     public IAuthenticationService authenticationService { get; set; }

     protected void Page_Load(object sender, EventArgs e)
     {
         // can start using authenticationService
     }
}