Simplify Dependency Injection In .NET 6 For Windows Forms Development

Dependency Injection In .NET 6

In the rapidly changing world of software development, one thing remains constant: the perpetual challenge of managing the complexity that naturally arises as applications grow in size and complexity. As our projects expand to encompass more features, functionalities, and interconnected parts, the need for maintainable, testable, and adaptable code becomes more critical than ever before.

Consider it this way: picture a sprawling metropolis, a city that started as a small village but has grown into a vast and intricate network of roads, buildings, and infrastructure. This city represents a software application, with each road and building symbolizing a component or piece of code.

In the early stages of the city’s development, it was relatively straightforward to navigate and manage. The roads were simple, and the buildings were few and far between. However, as time passed, the city grew in size and complexity. New roads were built, buildings sprouted up, and the once-simple layout became a labyrinth of interconnected streets and structures.

Similarly, in software development, a project that begins as a small, manageable codebase can quickly evolve into a sprawling application with many interconnected components, modules, and libraries.

Dependency Injection (DI) is a fundamental concept in modern software development that helps manage the complexity of large applications by promoting loose coupling between components. It’s widely used in .NET applications, including WinForms, to improve maintainability, testability, and code reuse. In this article, we’ll explore how to implement Dependency Injection in a .NET 6 Windows Forms application with real-world examples.

In this article, we explore dependency injection and how to implement it into Windows Forms Applications. The following topics will be covered in this article.

What is Dependency Injection?
Why Use Dependency Injection in Windows Forms?
Setting Up a .NET 6 Windows Forms Project
Implementing Dependency Injection
Registering Services
Resolving Dependencies
Constructor Injection
Property Injection
Conclusion

What is Dependency Injection?

Dependency Injection is a design pattern that enables the separation of concerns in an application by providing a way to inject dependencies (such as services, objects, or configurations) into a component rather than letting the component create them. This promotes modularity, testability, and code maintainability.

Why to Use Dependency Injection?

In Windows Forms applications, using Dependency Injection offers several advantages:

Testability: Components can be tested in isolation by injecting mock or fake dependencies, allowing for unit testing.
Loose Coupling: Dependencies are not hard-coded, making it easier to change or extend functionality without modifying existing code.
Readability and Maintainability: The code becomes more readable and maintainable as dependencies are explicitly defined and injected.
Code Reuse: Dependencies can be reused across multiple components.
Scalability: The application can scale by adding new services without affecting existing code.

Setting Up a .NET 6 Windows Forms Project

Before implementing Dependency Injection, create a .NET 6 Windows Forms project using Visual Studio or the .NET CLI. Ensure you have the necessary tools and SDK installed.

Visual Studio 2022
.NET 6 SDK
Windows Development Workload in Visual Studio

We will commence by creating a Windows Forms Project from Visual Studio.

Dependency Injection In .NET 6

Give a name to the project. I have named as DIWinFormsSample. Choose .Net Framework, .NET 6.

Now our Windows Forms application is created.

Implementing Dependency Injection

To implement DI in the above Windows Forms application, follow these steps:

Add Required NuGet Packages

In the WinForms project, add the following NuGet packages:

Microsoft.Extensions.DependencyInjection
Microsoft.Extensions.Hosting

Tips: better to get the latest version of NuGet Packages.

We will navigate program.cs file and add a function CreateHostBuilder, as shown below.

Create a host builder to build the service provider.

public static IServiceProvider ServiceProvider { get; private set; }
static IHostBuilder CreateHostBuilder()
{
    return Host.CreateDefaultBuilder()
        .ConfigureServices((context, services) => {
            services.AddTransient<IBlobStorageService, BlobStorageService>();
            services.AddTransient<IErrorMessageLog, ErrorMessageLog>();
            services.AddTransient<IFileMigrationService, FileMigrationService>();
            services.AddTransient<IAttachmentDataAccess, AttachmentDataAccess>();
            services.AddTransient<MainForm>();
        });
}

In the ConfigureServices method, use services.AddScoped<TInterface, TImplementation>() to register your services and interfaces. Replace IMyService and MyService with your actual interface and service implementation.

We will call the Host Builder to build the services provider in Main function as shown below:

var host = CreateHostBuilder().Build();
ServiceProvider = host.Services;

Application.Run(ServiceProvider.GetRequiredService<MainForm>());

Complete Program.cs class.

using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;

namespace DIWinFormsSample
{
    internal static class Program
    {
        /// <summary>
        ///  The main entry point for the application.
        /// </summary>
        [STAThread]
        static void Main()
        {
            // To customize application configuration such as set high DPI settings or default font,
            // see https://aka.ms/applicationconfiguration.
            ApplicationConfiguration.Initialize();
            var host = CreateHostBuilder().Build();
            ServiceProvider = host.Services;

            Application.Run(ServiceProvider.GetRequiredService<Form1>());
        }

        public static IServiceProvider ServiceProvider { get; private set; }
        /// <summary>
        /// Create a host builder to build the service provider
        /// </summary>
        /// <returns></returns>
        static IHostBuilder CreateHostBuilder()
        {
            return Host.CreateDefaultBuilder()
                .ConfigureServices((context, services) => {
                    //services.AddScoped<TInterface, TImplementation>();
                    services.AddTransient<Form1>();
                });
        }
    }
}

Now let’s create an interface and implement it.

IMessageService – Interface class MessageService – Implementation Class

IMessageService.cs

namespace DIWinFormsSample.Services
{
    public interface IMessageService
    {
        string GetSuccessMessage();
    }
}

MessageService.cs

namespace DIWinFormsSample.Services
{
    public class MessageService : IMessageService
    {
        public string GetSuccessMessage()
        {
            return "Successful Operation!!";
        }
    }
}

Now, we will register the service into container in program.cs file.

Dependency Injection In .NET 6

Let's just Rename Form1 into Mainform.

Code:

static IHostBuilder CreateHostBuilder()
  {
      return Host.CreateDefaultBuilder()
          .ConfigureServices((context, services) => {
              services.AddTransient<IMessageService, MessageService>();
              services.AddTransient<MainForm>();
          });
  }

Create and Inject Services

We have already created the Message service. In the Windows Forms or components, you can now inject services using constructor injection.

Sample:

public partial class MainForm : Form
{
    private readonly IMyService _myService;

    public MainForm(IMyService myService)
    {
        _myService = myService;
        InitializeComponent();
    }

    // ...
}

We will inject the MessageService in our MainForm through a constructor.

using DIWinFormsSample.Services;
namespace DIWinFormsSample
{
    public partial class MainForm : Form
    {
        private readonly IMessageService _messageService;
        public Form1(IMessageService messageService)
        {
            _messageService = messageService;
            InitializeComponent();
            lblMessage.Text = _messageService.GetSuccessMessage();
        }
    }
}

Output screen for the above solution.

Dependency Injection In .NET 6

Constructor Injection

Constructor injection is the preferred way to inject dependencies. It ensures that required dependencies are available when an object is created. In our example, the Form1 constructor expects an instance of IMessageService.

Alternatively, Property injection can be used when you need optional dependencies. You can create properties in your form and set them through the DI container. However, constructor injection is recommended for mandatory dependencies.

Complete Source code: GitHub.

Conclusion

Dependency Injection is a powerful technique for improving the structure, testability, and maintainability of .NET Windows Forms applications. With .NET 6, setting up DI has become easier than ever, thanks to Microsoft.Extensions.DependencyInjection library. By following the steps outlined in this article, you can harness the benefits of DI in your Windows Forms projects, making them more robust and maintainable.

Remember to register your services, use constructor injection for mandatory dependencies, and enjoy the benefits of a loosely coupled and easily testable application architecture.

References