Asp.NetCore启动过程

1.Program类

Main函数调用CreateHostBuilder（）方法，而CreateHostBuilder（）返回了IHostBuilder，IHostBuilder就是应用程序启动的核心接口

public class Program
{public static void Main(string[] args){CreateHostBuilder(args).Builder().Run();}public static IHostBuilder CreateHostBuilder(string[] args)=>Host.CreateDefaultBuilder(args).ConfigureAppConfiguration(builder=>{Console.WriteLine("ConfigureAppConfiguration");}).ConfigureServices(builder=>{Console.WriteLine("ConfigureServices");}).ConfigureHostConfiguration(builder=>{Console.WriteLine("ConfigureHostConfiguration");}).ConfigureWebHostDefaults(webBuilder=>{Console.WriteLine("ConfigureWebHostDefaults");webBuilder.UseStartup<StartUp>();})
}

2.Start Up

• 组成:
  1.构造函数
  2.ConfigureServices()
  3.Configure（）

public class Startup
{public Startup(Iconfiguration configuration){Console.WriteLine("Startup.Startup");Configureation = configuration;}public IConfiguration Configuration {get;set;}// 服务注册public void ConfigureServices(IServiceCollection services){Console.WriteLine("Startup.ConfigureServices");services.AddControllers();}// 注册中间件public void Configure(IApplicationBuilder app,IWebHostEnvironment env){Console.WriteLine("Startup.Configure");....}
}

• 启动运行,输出结果如下:

ConfigureWebHostDefaults
ConfigureHostConfiguration
ConfigureAppConfiguration
ConfigureServices
Startup.Startup
Startup.ConfigureServices
Startup.Configure

• 说明:

执行顺序
1.ConfigureWebHostDefaults
注册程序必要的几个组件,如配置组件,容器组件

2.ConfigureHostConfiguration
配置应用程序启动是必要的配置。比如需要监听的端口，监听的URL地址，这里也可以嵌入自己的个性化配置内容，注入到框架中

3.ConfigureAppConfiguration
用来配置我们自己的配置文件，供应用程序来读取。这些配置将在后续应用程序执行过程中间被每个组件读取

4.ConfigureServices、ConfigureLogging、Startup、Startup.ConfigureServices
用来往容器中注册注入我们的应用的组件

5.Startup.Configure
用来注入中间件,处理HttpContext整个请求过程的

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这里在Program中的webBuilder.UseStartup();代码不是必需的,只是为了让代码结构更合理。可以在CreateHostBuilder直接进行Configure和ConfigureServices注册

public static IHostBuilder CreateHostBuilder(string[] args)=>Host.CreateDefaultBuilder(args).ConfigureAppConfiguration(builder=>{Console.WriteLine("ConfigureAppConfiguration");}).ConfigureServices(builder=>{Console.WriteLine("ConfigureServices");}).ConfigureHostConfiguration(builder=>{Console.WriteLine("ConfigureHostConfiguration");}).ConfigureWebHostDefaults(webBuilder=>{Console.WriteLine("ConfigureWebHostDefaults");webBuilder.ConfigureServices(services=>{services.AddController();});webBuilder.Configure(app=>{})// webBuilder.UseStartup<StartUp>();})