Prevent duplicated service registration

program.cs

using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using System.Collections;
using System.Diagnostics.CodeAnalysis;

namespace CompanyName;

internal class Program
{
	private static void Main(string[] args)
	{
		var appBuidler = Host.CreateApplicationBuilder();

		appBuidler.ConfigureContainer(new ConstrainedServiceProviderFactory());

		appBuidler.Services.AddSingleton<IService, Serivce1>();
		appBuidler.Services.AddSingleton<IService, Serivce2>();

		var app = appBuidler.Build();

		app.Run();
	}
}

interface IService
{
}

class Serivce1 : IService
{

}

class Serivce2 : IService
{

}


internal class ConstrainedServiceProviderFactory : IServiceProviderFactory<ConstrainedServiceProviderFactory.ContainerBuilder>
{
	internal class ContainerBuilder
	{
		public ContainerBuilder(IServiceCollection services)
		{
			Services = services;
		}

		public IServiceCollection Services { get; }
	}

	public ContainerBuilder CreateBuilder(IServiceCollection services)
	{
		return new ContainerBuilder(services);
	}

	public IServiceProvider CreateServiceProvider(ContainerBuilder containerBuilder)
	{
		CheckConstraints(containerBuilder.Services);
		return containerBuilder.Services.BuildServiceProvider();
	}

	private void CheckConstraints(IServiceCollection services)
	{

		/*
		var lookups = services.Where(x => x.ServiceType.Namespace == "CompanyName").ToLookup(x => (x.ServiceType, x.ServiceKey));
		foreach (var service in lookups.Where(x => x.Count() > 1))
		{
			foreach (var item in service)
			{
				Console.WriteLine($"{item.ServiceType.Name} + {item.ServiceKey}");
			}
		}
		*/

		var registrations = new Dictionary<Type, ServiceDescriptor>();
		foreach (var item in services.Where(x => x.ServiceType.Namespace == "CompanyName"))
		{
			if (!registrations.TryAdd(item.ServiceType, item))
			{
				var existing = registrations[item.ServiceType];
				throw new Exception($"Can not add Service {item.ServiceType.Name} implemented as {item.ImplementationType?.Name} because it is already registered as {existing.ImplementationType?.Name}");
			}
		}
	}
}