Implementing Dependency Injection In . NET Core Console Applications

In this post I will show you how to configure DI in .net core application. .Net core provides out of the box features Dependency injection.

What is Dependency Injection

As per the Wikipedia

In software engineering, dependency injection is a technique in which an object receives other objects that it depends on. These other objects are called dependencies. In the typical “using” relationship the receiving object is called a client, and the passed (that is, “injected”) purpose is called a service.

Before .NET core developers used open-source DI container to achieve the loose coupling in their applications. Below are a few popular DI container used in .net application

• Castle Windsor
• StructureMap
• Unity
• Autofac

Now in .net core, DI is a first-class citizen. .Net Core exposed two classes IServiceProvider and ServiceCollection to implement the DI in .net core application.
Let’s start the coding.

Step1

• Create a new console application and add two interfaces IHtmlService and IPrintService as shown below

public interface IHtmlService
{
	void GenerateHtml();
}

public interface IPrintService
{
	void Print();
}

Step2

• Provide the implementation for this two interface

public class PrintService : IPrintService
{
	private readonly IHtmlService _fooService;
	public PrintService(IHtmlService fooService)
	{
		_fooService = fooService;
	}

	public void Print()
	{


		_fooService.GenerateHtml();

	}
}

public class HtmlService : IHtmlService
{
	private readonly ILogger<HtmlService> _logger;

	public HtmlService(ILoggerFactory loggerFactory)
	{
		_logger = loggerFactory.CreateLogger<HtmlService>();

	}

	public void GenerateHtml()
	{

		_logger.LogInformation($"Generating HTML");
	}
}

Step3

• Create a startup class in your application and add the following code. Here we are creating instance of ServiceCollection class and adding the dependency to the collection.

public class Startup
{


	public static ServiceProvider Configure()
	{
		var provider = new ServiceCollection()
					.AddTransient<IHtmlService, HtmlService>()
					.AddLogging(fs => fs.AddConsole())
					.AddTransient<IPrintService, PrintService>()
					.BuildServiceProvider();
		return provider;
	}

}

IServiceProvider is the simple built-in container that is included in ASP.NET Core that supports constructor injection by default.

Step4

• Go to Main method and paste the following code

void Main()
{

	var container = Startup.Configure();
	var print = container.GetService<IPrintService>();
	print.Print();
}