A basic C sharp web app example

HelloController.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Mvc;

namespace MyApp.Controllers {
    [ApiController]
    //path: "/hello"
    //the same as the Controller name
    //If you mistype the "HelloControer" (it won't be treated as a controller)
    [Route("[controller]")]
    public class HelloController : ControllerBase {
        //Can't access in "/hello/nickname"
        //[HttpGet("{nickname}/{another}")]
        //[HttpGet("{nickname}")]
        [HttpGet]
        // https://docs.microsoft.com/en-us/aspnet/core/web-api/advanced/formatting?view=aspnetcore-3.1
        public IActionResult WhaterveYouWannaCallIt([FromQuery]string name, [FromRoute]string nickname,[FromRoute] string another) {
            var hw = $"Hello {nickname}";
            //Http State Code
            return Ok(hw);
        }
    }
}

Program.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.Hosting;
using Microsoft.Extensions.Logging;
//它只做一件事, 就是创建一个HostBuilder, 从Startup.cs调取配置文件, 总之, 不用关心它(大概)

//命名空间就是你的项目名称, 自动创建的, 其实你想叫啥都可以啦. 
namespace MyApp {
    public class Program {
        //你的Main函数
        public static void Main(string[] args) {
            CreateHostBuilder(args).Build().Run();
        }

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

RabbitController.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text.Json;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Mvc;
using MyApp.Models;

namespace MyApp.ControllersOrSomething {
    //用方括号括起来的大概是修饰器(不对叫做Attributes)
    // https://docs.microsoft.com/en-us/dotnet/csharp/programming-guide/concepts/attributes/
    [ApiController]
    //Route, 括号里面的是其Path, [controller]就是用其**类**名称替代
    //和[Route("/rabbit")]是等效的
    [Route("[controller]")]
    //别拼错Controller了, 拼成别的是不会认的
    public class RabbitController : ControllerBase {

        //大家很熟悉的Get方法
        [HttpGet]
        //一个实现ActionResult的方法. Index为方法名(叫啥都行)
        public IActionResult Index() {
            //可以直接读Req和Res
            var req = Request;
            var res = Response;
            res.StatusCode = 404;
            res.ContentType = "application/json";
            //匿名对象
            var anonymous = new { Code = 404, Description = "I'm a rabbit, but I'm lost" };
            //dynamic类型
            // https://docs.microsoft.com/zh-tw/dotnet/csharp/programming-guide/types/using-type-dynamic
            var json = JsonSerializer.Serialize<dynamic>(anonymous);
            res.WriteAsync(json);

            return NotFound();//这里的Return好像没啥卵用, 因为直接写到了Res中. 
            //这也不是很MVC, 顺便一提
        }
    }
}

Startup.cs

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.AspNetCore.HttpsPolicy;
using Microsoft.AspNetCore.Mvc;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using Microsoft.Extensions.Logging;

//用户自定义的Models, 在后文会用到的
using MyApp.Models;

namespace MyApp {
    // https://docs.microsoft.com/zh-tw/aspnet/core/fundamentals/?view=aspnetcore-3.1&tabs=windows
    public class Startup {
        //看不懂, 大概是做一些不太明白的Configuration
        //Startup 的 Constructor
        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.
        //这个方法是用来向Container中添加Services的
        //重点来了, 这个地方用于添加各种Services
        //用于Dependency Injection
        public void ConfigureServices(IServiceCollection services) {
            //Bind all the controller
            //I mean all the controller
            //所有的API Controller, 类名后边带Controller的都会被绑定上
            services.AddControllers();

            //各种服务, 整不明白, 添加服务之后还得到下面加路由
            //services.AddRazorPages();
            //services.AddSignalRCore();
        }

        // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
        //配置一些HTTP相关的玩意, 也是重头戏. 
        public void Configure(IApplicationBuilder app, IWebHostEnvironment env) {
            if (env.IsDevelopment()) {
                //如果在开发环境那就显示专供开发者的ExceptionPage
                //好像是在launchSettings里边设置的? 
                app.UseDeveloperExceptionPage();
            }
            //和HTTPS有关的玩意
            // https://docs.microsoft.com/en-us/aspnet/core/security/enforcing-ssl?view=aspnetcore-3.1&tabs=visual-studio
            app.UseHttpsRedirection();
            //[ASP.NET Core 3.0 中 app.UseRouting 与 app.UseEndpoints 的区别是什么](https://q.cnblogs.com/q/115276/)
            app.UseRouting();
            //用于验证的中间件
            //app.UseAuthorization was added to the templates to show the order authorization middleware must be added. 
            //If the app doesn't use authorization, you can safely remove the call to app.UseAuthorization.
            app.UseAuthorization();
            app.UseEndpoints(endpoints => {
                //Add router for all the controller
                //和上边的services.AddControllers()一样, Map所有的Controllers的endpoints
                endpoints.MapControllers();
                //各种各样的服务
                //endpoints.MapRazorPages();
                //endpoints.MapBlazorHub();

                //这就有点意思了, 是不是想起了
                //app.get("/anotherhello",(req,res)=>{})
                //和各种类sinatra框架的写法很像了
                //但是C#并不鼓励你这么写, 这不MVC
                endpoints.MapGet("/anotherhello", (content) => {
                    var req = content.Request;
                    var res = content.Response;
                    var path = req.Path;
                    var query = req.QueryString;
                    var toDo = new ToDoItem { Id = 12345, Name = "hello", IsComplete = false }.ToString();
                    return content.Response.WriteAsync($"{toDo} from {path}, {query}");
                });
            });
        }
    }
}

ToDoItem.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text.Json;
using System.Threading.Tasks;

namespace MyApp.Models {
    public class ToDoItem {
        //如果用VS的话创建类属性可以直接用
        //prop 然后点两下Tap完事
        public long Id { get; set; }
        public string Name { get; set; }
        public bool IsComplete { get; set; }
        //覆写了ToString()方法, 使其JSON化
        public override string ToString() {
            //可选的类型声明
            //return JsonSerializer.Serialize(this);
            //我猜用尖括号括起来的是输入值的类, 但是我没有证据. 
            //Serialize 相当于json.stringify或者json.Marshal
            return JsonSerializer.Serialize<ToDoItem>(this);
        }
    }
}