在ASP.NET Core 5 MVC中，不再需要使用ConfigureServices方法来配置依赖注入，而是直接在Program.cs中添加对服务的配置。下面是一个示例代码：

using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;

namespace MyProject
{
    public class Startup
    {
        public IConfiguration Configuration { get; }

        public Startup(IConfiguration configuration)
        {
            Configuration = configuration;
        }

        public void ConfigureServices(IServiceCollection services)
        {
            // 添加服务
            services.AddMvc();
        }

        public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
        {
            // 启用MVC中间件
            app.UseRouting();
            app.UseEndpoints(endpoints =>
            {
                endpoints.MapControllerRoute(
                    name: "default",
                    pattern: "{controller=Home}/{action=Index}/{id?}");
            });
        }
    }

    public class Program
    {
        public static void Main(string[] args)
        {
            CreateHostBuilder(args).Build().Run();
        }

        public static IHostBuilder CreateHostBuilder(string[] args)
        {
            return Host.CreateDefaultBuilder(args)
                .ConfigureWebHostDefaults(webBuilder =>
                {
                    webBuilder.UseStartup();
                });
        }
    }
}

在上述示例代码中，ConfigureServices方法被移除了，而把服务的配置添加到了Program.cs文件中的CreateHostBuilder方法里面。这样的重构可以更好地保持代码的简洁和可读性，同时更好地实现依赖注入的灵活性。