Startup.cs

using System.Diagnostics;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using Unity;
using Unity.Lifetime;

namespace WebApplication1
{
    public class Startup
    {
        public Startup(IConfiguration configuration)
        {
            Configuration = configuration;
        }

        public IConfiguration Configuration { get; }

        // This method gets called by the runtime. Use this method to add services to the container.
        public void ConfigureServices(IServiceCollection services)
        {
            services.AddControllers();
        }

        public void ConfigureContainer(IUnityContainer container)
        {
            var webHostEnvironment = container.Resolve<IWebHostEnvironment>();
            Debug.Assert(webHostEnvironment != null, "webHostEnvironment is null");

            container.RegisterFactory<ITest>(c =>
            {
                var webHost = c.Resolve<IWebHostEnvironment>();
                return new Test(webHost.ContentRootPath);
            }, new SingletonLifetimeManager());

            var test = container.Resolve<ITest>();
        }

        // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
        public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
        {
            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
            }

            app.UseHttpsRedirection();

            app.UseRouting();

            app.UseAuthorization();

            app.UseEndpoints(endpoints =>
            {
                endpoints.MapControllers();
            });
        }
    }
}