Add project files.

WinGreedWPF/StartupHelpers/AbstractFactory.cs

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+using System;
+
+namespace WinGreedWPF.StartupHelpers;
+
+public class AbstractFactory<T> : IAbstractFactory<T>
+{
+    private readonly Func<T> _factory;
+
+    public AbstractFactory(Func<T> factory)
+    {
+        _factory = factory;
+    }
+
+    public T Create()
+    {
+        return _factory();
+    }
+}

WinGreedWPF/StartupHelpers/IAbstractFactory.cs

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+namespace WinGreedWPF.StartupHelpers
+{
+    public interface IAbstractFactory<T>
+    {
+        T Create();
+    }
+}

WinGreedWPF/StartupHelpers/ServiceExtensions.cs

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+using Microsoft.Extensions.DependencyInjection;
+using System;
+
+namespace WinGreedWPF.StartupHelpers;
+
+public static class ServiceExtensions
+{
+    public static void AddFormFactory<TForm>(this IServiceCollection services)
+        where TForm : class
+    {
+        services.AddTransient<TForm>();
+        services.AddSingleton<Func<TForm>>(x => () => x.GetService<TForm>()!);
+        services.AddSingleton<IAbstractFactory<TForm>, AbstractFactory<TForm>>();
+    }
+}