Scoping which controller types are registered in aspnet core

MvcExtensions.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Reflection;
using Microsoft.AspNetCore.Mvc.ApplicationParts;
using Microsoft.Extensions.DependencyInjection;

namespace MyApp
{
    public static class MvcExtensions
    {
        public static void UseControllersWithinTypeNamespace(
            this ApplicationPartManager partManager,
            Type type)
        {
            partManager.ApplicationParts.Clear();
            partManager.ApplicationParts.Add(new NamespaceApplicationPart(type));
        }

        public static void UseControllersWithinTypeNamespace(
            this IMvcCoreBuilder mvcCoreBuilder,
            Type type)
        {
            mvcCoreBuilder
                .ConfigureApplicationPartManager(partManager => partManager.UseControllersWithinTypeNamespace(type));
        }

        private class NamespaceApplicationPart : ApplicationPart, IApplicationPartTypeProvider
        {
            public NamespaceApplicationPart(Type namespaceType)
            {
                Name = namespaceType.Namespace;

                Types = namespaceType
                    .Assembly
                    .DefinedTypes
                    .Where(t => t.Namespace != null && t.Namespace.StartsWith(namespaceType.Namespace))
                    .ToArray();
            }

            public override string Name { get; }

            public IEnumerable<TypeInfo> Types { get; }
        }
    }
}