Program.cs中：

       第一步：在var builder = WebApplication.CreateBuilder(args);的后面添加上：

        

var startup = new Startup(builder.Configuration);
startup.ConfigureServices(builder.Services);

        第二步：在var app = builder.Build();的后面添加上：

        

startup.Configure(app, builder.Environment);

 Startup.cs:

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