ApplicationBase and IOC

ApplicationBase is the entry point for any Tharga.Wpf application. It hosts a Microsoft.Extensions.Hosting builder, configures the dependency-injection container, and exposes a static GetService<T>() accessor for code paths where constructor injection is not available.

Registering services

Override Register in your App class:

protected override void Register(HostBuilderContext context, IServiceCollection services)
{
    services.AddTransient<IOrderService, OrderService>();
    services.AddSingleton<ICustomerCache, CustomerCache>();
}

HostBuilderContext exposes Configuration (an IConfiguration) so you can register against appsettings.json-style configuration the same way an ASP.NET host does.

Resolving services

Two paths:

Constructor injection — ViewModels (anything registered or marked with IViewModel) receive registered services through their constructors:

public class OrderViewModel(IOrderService orderService) : ViewModelBase
{
    private readonly IOrderService _orderService = orderService;
}

Static accessor — for code-behind or static helpers:

var orderService = ApplicationBase.GetService<IOrderService>();

If the requested type was not registered, GetService<T> throws TypeNotRegisteredException. The accessor is safe to call from any thread; the underlying provider is the same instance that was built during startup.

MVVM binding helper — ViewModelProvider

Wire a View to its ViewModel declaratively in XAML without manually constructing or setting DataContext:

<UserControl
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:wpf="clr-namespace:Tharga.Wpf;assembly=Tharga.Wpf"
    xmlns:local="clr-namespace:MyApp.Views"
    DataContext="{wpf:ViewModelProvider local:OrderViewModel}">
</UserControl>

The ViewModelProvider markup extension constructs the ViewModel through the DI container so any injected dependencies resolve. Pair this with IViewModel (see below) so the ViewModel does not need an explicit services.AddTransient<OrderViewModel>() line.

IViewModel — auto-registration

Any type that implements the marker interface Tharga.Wpf.IViewModel is auto-registered in DI during host build, so you do not need to add it to services manually.

public class OrderViewModel : ViewModelBase, IViewModel
{
    public OrderViewModel(IOrderService orderService) { ... }
}

If your ViewModels live in a different assembly than the App class, register that assembly in Options:

protected override void Options(ThargaWpfOptions options)
{
    options.UseAssembly(typeof(OrderViewModel).Assembly);
}

ApplicationBase's startup scans both its own assembly and any assemblies added via UseAssembly for IViewModel implementations.

ViewModel base class

ViewModelBase provides:

• INotifyPropertyChanged plumbing with a SetField helper.
• RelayCommand / RelayCommand<T> for binding commands without writing custom command classes.

public class CounterViewModel : ViewModelBase
{
    private int _count;
    public int Count
    {
        get => _count;
        set => SetField(ref _count, value);
    }

    public ICommand IncrementCommand => new RelayCommand(_ => Count++);
}