创建项目

在VS中创建一个空的Asp.Net Core 3.1 Web应用程序

Program.cs

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

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

Startup.cs

    public class Startup
    {
        //注册服务
        public void ConfigureServices(IServiceCollection services)
        {
        }

        // 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.UseRouting();

            app.UseEndpoints(endpoints =>
            {
                endpoints.MapGet("/", async context =>
                {
                    await context.Response.WriteAsync("Hello World!");
                });
            });
        }
    }

注册服务

Startup.cs

        //注册服务
        public void ConfigureServices(IServiceCollection services)
        {
            services.AddControllersWithViews(); //做Web 应用程序，使用视图页面
            services.AddControllers(); //做webApi应用
        }

Asp.Net Core 3.x (一) 创建项目