Simple.WPF.DI

Install

dotnet add package Simple.WPF.DI

Since WPF is Windows only, you need a .Net-windows project.

Usage

Top-level Program.cs:

using Simple.WPF.DI;

Thread.CurrentThread.SetApartmentState(ApartmentState.Unknown);
Thread.CurrentThread.SetApartmentState(ApartmentState.STA);

var builder = WpfApp.CreateBuilder();

builder.Services.AddSingleton<MainViewModel>();

var app = builder
    .UseApp<App>()
    .UseWindow<MainWindow>()
    .Build();

app.Run();

Inject a MainViewModel into the MainWindow:

public partial class MainWindow : Window
{
    private readonly MainViewModel _mainViewModel;

    public MainWindow(MainViewModel mainViewModel)
    {
        InitializeComponent();
        _mainViewModel = mainViewModel;
        DataContext = mainViewModel;
    }
}

When starting with the default WPF project template, a different entry-point is already defined on the App.
This conflict with the top-level Program.cs which is now used as and entry point that sets up Dependency Injection and start the WPF GUI. Remove this by changing the "App.xml" properties to the "Page" build action. This prevents and error that there are 2 entry points in the application.

Inject into UserControls

It's not possible in WPF to use contructor injection. One possible workaround is to create a static ServiceProvider in the App class.

public partial class App : Application
{
	public App(IServiceProvider serviceProvider)
	{
		ServiceProvider = serviceProvider;
	}

	public static IServiceProvider ServiceProvider { get; private set; } = default!;
}

Use this ServiceProvider in the contructor of the UserControl.

public partial class MyUserControl : UserControl
{
    private readonly MainViewModel = mainViewModel;

    public MyUserControl()
    {
        mainViewModel = App.ServiceProvider.GetRequiredService<MainViewModel>();
    }
}

IHostedService

IHostedSerice's that are registered are not automatically start when running the app. These services can be started manually by first resolving them from the ServiceProvider:

IEnumarable<IHosteedService> hostedServices = _services.GetServices<IHostedService>()

And starting them before calling app.Run(), and stopping them after app.Run() completed using StartAsync(token) and StopAsync(token). Consider creating extention methods on WpfApp to start / stop these hosted services.