是不是使用的是net core 3+？课程是基于2.2的，所以会跟3+有所不同。试试： "services.AddMvc(option => option.EnableEndpointRouting = false) .AddNewtonsoftJson();", 意思就是默认禁用Endpoint Routing

感觉像是依赖没添加，截图留下startup文件代码，我可以仔细看看。

要把

endpoints.MapGet("/", async context =>

                {

                    await context.Response.WriteAsync("Hello World!");

                });

这句话删掉，否则就会覆盖HomeController里的设置

 app.UseEndpoints(endpoints =>

            {

                endpoints.MapGet("/", async context =>

                {

                    await context.Response.WriteAsync("Hello World!");

                });

                endpoints.MapDefaultControllerRoute();

            });

3.1版本,这么写就OK啦,很简单!

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!");

                });

                endpoints.MapControllerRoute(

                    name: "default",

                    pattern: "{controller=Home}/{action=Index}/{id?}");

            });

        }

这是asp.net core 3.1的添加方法,用这个就行了

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Http;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;

namespace CityGarden
{
    public class Startup
    {
        // This method gets called by the runtime. Use this method to add services to the container.
        // For more information on how to configure your application, visit https://go.microsoft.com/fwlink/?LinkID=398940
        public void ConfigureServices(IServiceCollection services)
        {
            services.AddMvc();
        }

        // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
        //请求通道都是通过IApplicationBuilder创建的。
        //每个中间件都可以截获、传递、修改请求对象，输出响应对象。
        //特定情况下某些中间件可以做短路处理，直接像前端输出响应对象。
        public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
        {
            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
            }
            //自定义路由

            /*app.UseMvc(route =>
            {
                route.MapRoute("default","{controller=Home}/{action=index}/{id?}");
            });*/

            app.Map("/test", build =>
            {
                build.Run(async context =>
                {
                    await context.Response.WriteAsync("Hello form test!");
                });
            });

        }
    }
}