Dotnetdi

Registering a Service

Constructor Injection

With constructor Injection we define the list of required dependencies as parameters of the constructor for the class

class IainsController : Controller
{
    private IIainsWidget _iainsWidget;

    public IainsController(IIainsWidget iainsWidet)
    {
       _iainsWidget = iainsWidget;
    }
}

Registering a Service

In ASP Core the service must be registered with the IServiceCollection in the startup class configureServices.

public void ConfigureServices(IServiceCollection services)
{
    services.AddTransient<IIainsWidget, IainsWidget>();
}

Microsoft Dependency Injection Container

Introduction

When building a site try and build a dependency graph which will help determine what services you will need

Configuration

An options class:

• Must be non-abstract with a public parameterless constructor.
• All public read-write properties of the type are bound.
• Fields are not bound. In the preceding code, Position is not bound. The Position property is used so the string "Position" doesn't need to be hard coded in the app when binding the class to a configuration provider.

Example

public class PositionOptions
{
    public const string Position = "Position";

    public string Title { get; set; }
    public string Name { get; set; }
}

Now this can be passed using Dependency Injection using the Startup

public void ConfigureServices(IServiceCollection services)
{
    services.Configure<PositionOptions>(Configuration.GetSection(
                                        PositionOptions.Position));
    services.AddRazorPages();
}

Add in the Controller

public void HomeController : Controller
{
    private PostionalOptions _positionalOptions;

    public HomeController(IOptions<PositionOptions> options)
    {
        _positionalOptions = options;
    } 
}