Net Core的启动项Program

在WebApi的项目中和在控制台中都是有Program启动项的身影

API中基本就是下面的这样，基本是不动，而是把配置的信息，放在StartUp中
namespace HubAPI
{
    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>();//可以看到这里是去出发StartUp这个类了。
                });
    }
}

namespace HubAPI
{
    public class Startup
    {
        public Startup(IConfiguration configuration)
        {
            Configuration = configuration;
        }
        IConfiguration 是用来加载配置值的，可以加载内存键值对、JSON或XML配置文件，我们通常用来加载缺省的appsettings.json .
        public IConfiguration Configuration { get; } 
  
        下面这个参数Services ：指定服务描述符集合的协定(就是说，你需要的服务就是要在这个里面进行Add，下面的每一个服务都是Add开头的)
        public void ConfigureServices(IServiceCollection services)
        {
            services.AddControllers();
            //这个是绑定GetSection--》AppSetting
            services.Configure<AppSettings>(Configuration.GetSection("AppSettings"));/

            绑定数据库db，就这个Configuration就可以读取到Appsettings.Json的数据了
            string conn = Configuration.GetConnectionString("db");
            services.AddDbContext<HubData.ACC_MINIEHUBContext>
            (
                p => p.UseSqlServer(conn).EnableSensitiveDataLogging()
             );            

            //service bus
            services.AddSingleton<ITopicClient>(x =>
            {
                return new TopicClient(Configuration.GetConnectionString("azure"), "servicesbus2topic1");
            });            
            services.AddApiVersioning(option =>
            {
                option.ReportApiVersions = true;
                option.AssumeDefaultVersionWhenUnspecified = true;
                option.DefaultApiVersion = new Microsoft.AspNetCore.Mvc.ApiVersion(1, 0);
            });
            services.AddHttpClient();
            services.AddTransient<HubService.SOService>();            
        }
       
        public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
        {
            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
            }
            app.UseHttpsRedirection();
            app.UseRouting();
            app.UseAuthorization();
            app.UseEndpoints(endpoints =>
            {
                endpoints.MapControllers();
            });
        }
    }
}

{
  "ConnectionStrings": {
    "db": "锄禾日当午"    
  },

  "AppSettings": {   
    "静夜思": "李白",
    "悯农": "李绅"
  },

  "Logging": {
    "LogLevel": {
      "Default": "Trace",
      "Microsoft": "Information"
    }
  },
  "AllowedHosts": "*"
}

下面说下控制台应用程序的配置怎么搞

using HubDatetime;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using Microsoft.Extensions.Logging;
using System;

namespace HubBackend
{
    class Program
    {
        private static IConfiguration Configuration { get; set; }
        static void Main(string[] args)
        {
            //IHostBuilder是供库和应用程序初始化、生成和运行主机的主要组件：
            //就认为是启动的地基,一切都在HostBuildr上面建立起来,
            //Host主机，Builder 建设
            var buildr = new HostBuilder();
         >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
            //获取环境变量
            //var environment = Environment.GetEnvironmentVariable("ASPNETCORE_ENVIRONMENT");
            //加载配置文件ConfigurationBuilder
            这个写法，可以参考：https://www.jianshu.com/p/b9416867e6e6
            var config = new ConfigurationBuilder()
                        .AddJsonFile("appsettings.json", optional: true, reloadOnChange: true)
                      //.AddJsonFile($"appsettings.{environment}.json", optional: true, reloadOnChange: true)
                        .AddEnvironmentVariables()
                        .Build();
          >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
            //配置sb
            buildr.ConfigureWebJobs((h, b) =>
                                        {
                                            b.AddAzureStorageCoreServices();
                                            b.AddServiceBus(c =>
                                            {
                                                c.ConnectionString = h.Configuration.GetConnectionString("acc_azure");
                                                c.MessageHandlerOptions.MaxConcurrentCalls = 1;
                                            });
                                        }
                                   );
            >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
            //加入该句会把执行过程中的语句在控制台输出
            buildr.ConfigureLogging((context, b) =>
            {
                b.AddConsole();
            });
             >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
            //h是HostBuilderContext,也可以理解成上下文，这个上下文是主机Host与数据仓库与Configuration配置文件做交互
            //services是IServiceCollection 
            //配置服务(就是配置数据库,Service等等)
            buildr.ConfigureServices((h, services) =>
            {               
                Configuration = h.Configuration;                
                services.AddOptions(); 
                //绑定数据库hub
                string hub = h.Configuration.GetConnectionString("hub");
                services.AddDbContext<HUBContext>
                (
                    p => p.UseSqlServer(hub)
                 );
                services.AddHttpClient();
                //配置生命周期
                services.AddTransient<HubService.SO>();
                services.AddTransient<HubService.Inventory>();
                services.AddSingleton(Configuration);              
                services.AddSingleton<HubDatetime.IStandardDateTime, HubDatetime.StandardDateTime>();
            });
            >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
            //HostBuilder 组建起来了,"变形金刚要站起来"了,Build();
            var host = buildr.Build();
            using (host)
            {
                host.Run();//运行程序
            }
        }
    }
}