configuring-dependency-injection

# Dependency Injection and GenericHost Usage

A guide on using Dependency Injection and GenericHost in .NET projects.

## Project Structure

The templates folder contains a .NET 9 WPF project example.

```
templates/
├── WpfDISample.App/           ← WPF Application Project
│   ├── Views/
│   │   ├── MainWindow.xaml
│   │   └── MainWindow.xaml.cs
│   ├── App.xaml
│   ├── App.xaml.cs
│   ├── GlobalUsings.cs
│   └── WpfDISample.App.csproj
└── WpfDISample.ViewModels/    ← ViewModel Class Library (UI framework independent)
    ├── MainViewModel.cs
    ├── GlobalUsings.cs
    └── WpfDISample.ViewModels.csproj
```

## Core Principles

- **Implement dependency injection using Microsoft.Extensions.DependencyInjection**
- **Use GenericHost (Microsoft.Extensions.Hosting) as the default**
- **Apply service injection through Constructor Injection**

## Console and General Projects - Program.cs

```csharp
// Program.cs
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;

// Configure DI using GenericHost
var host = Host.CreateDefaultBuilder(args)
    .ConfigureServices((context, services) =>
    {
        // Register services
        services.AddSingleton<IUserRepository, UserRepository>();
        services.AddScoped<IUserService, UserService>();
        services.AddTransient<IEmailService, EmailService>();

        // Register main application service
        services.AddSingleton<App>();
    })
    .Build();

// Get service through ServiceProvider
var app = host.Services.GetRequiredService<App>();
await app.RunAsync();

// Application class - Constructor Injection
public sealed class App(IUserService userService, IEmailService emailService)
{
    private readonly IUserService _userService = userService;
    private readonly IEmailService _emailService = emailService;

    public async Task RunAsync()
    {
        // Use injected services
        var users = await _userService.GetAllUsersAsync();

        foreach (var user in users)
        {