一、前言
这篇文章就是从能看到地方去学习Core，没有很深奥，也没有很难懂，现在我们开始吧。
二、构建项目，引发思考
创建项目的步骤真的很简单，你要是不会，我真也没法了，我这是创建的MVC的项目。
接下来我们开始找不同，这个小学生也会的东西，我相信也难不到大家，这里我们主要说重点的不同:
1. 少了Content和Scripts文件夹，多了wwwroot；
2.少了配置文件web.config,多了appsettings.json；
3.少了App_Start文件夹，多了Program.cs和Startup.cs；
后面确实，实现了前面的功能，接下来引发下我们的思考，带着这些问题我们来学习Core：
配置文件：
1.为什么appsettings.json能默认成为配置文件？
2.怎么读取配置文件？
3.Global.asax如何在core中体现；
DI:
1.为什么全部能按照接口的方式进行注入？
2.怎么替换掉内置的DI？
MVC:
1.Core的请求和MVC的请求有什么不同？
2.Core的认证和授权怎么处理？
怀着这些问题我们来简单结合源码分析下,另外最后我们在上传一个简单的增删改查项目完成我们项目结束。
三、配置文件
GitHub地址:https://github.com/aspnet/MetaPackages/tree/dev/src/Microsoft.AspNetCore
1.为什么appsettings.json能默认成为配置文件？
这个问题看下主要部分在这个地址下面:https://github.com/aspnet/MetaPackages/blob/dev/src/Microsoft.AspNetCore/WebHost.cs,我截取下主要代码；
?????public static IWebHostBuilder CreateDefaultBuilder(string[] args) ???????{ ???????????var builder = new WebHostBuilder(); ???????????if (string.IsNullOrEmpty(builder.GetSetting(WebHostDefaults.ContentRootKey))) ???????????{ ???????????????builder.UseContentRoot(Directory.GetCurrentDirectory()); ???????????} ???????????if (args != null) ???????????{ ???????????????builder.UseConfiguration(new ConfigurationBuilder().AddCommandLine(args).Build()); ???????????} ???????????builder.UseKestrel((builderContext, options) => ???????????????{ ???????????????????options.Configure(builderContext.Configuration.GetSection("Kestrel")); ???????????????}) ???????????????.ConfigureAppConfiguration((hostingContext, config) => ???????????????{ ???????????????????var env = hostingContext.HostingEnvironment; ???????????????????config.AddJsonFile("appsettings.json", optional: true, reloadOnChange: true) ?????????????????????????.AddJsonFile($"appsettings.{env.EnvironmentName}.json", optional: true, reloadOnChange: true); ???????????????????if (env.IsDevelopment()) ???????????????????{ ???????????????????????var appAssembly = Assembly.Load(new AssemblyName(env.ApplicationName)); ???????????????????????if (appAssembly != null) ???????????????????????{ ???????????????????????????config.AddUserSecrets(appAssembly, optional: true); ???????????????????????} ???????????????????} ???????????????????config.AddEnvironmentVariables(); ???????????????????if (args != null) ???????????????????{ ???????????????????????config.AddCommandLine(args); ???????????????????} ???????????????}) ???????????????.ConfigureLogging((hostingContext, logging) => ???????????????{ ???????????????????logging.AddConfiguration(hostingContext.Configuration.GetSection("Logging")); ???????????????????logging.AddConsole(); ???????????????????logging.AddDebug(); ???????????????}) ???????????????.ConfigureServices((hostingContext, services) => ???????????????{ ???????????????????// Fallback ???????????????????services.PostConfigure<HostFilteringOptions>(options => ???????????????????{ ???????????????????????if (options.AllowedHosts == null || options.AllowedHosts.Count == 0) ???????????????????????{ ???????????????????????????// "AllowedHosts": "localhost;127.0.0.1;[::1]" ???????????????????????????var hosts = hostingContext.Configuration["AllowedHosts"]?.Split(new[] { ‘;‘ }, StringSplitOptions.RemoveEmptyEntries); ???????????????????????????// Fall back to "*" to disable. ???????????????????????????options.AllowedHosts = (hosts?.Length > 0 ? hosts : new[] { "*" }); ???????????????????????} ???????????????????}); ???????????????????// Change notification ???????????????????services.AddSingleton<IOptionsChangeTokenSource<HostFilteringOptions>>( ???????????????????????new ConfigurationChangeTokenSource<HostFilteringOptions>(hostingContext.Configuration)); ???????????????????services.AddTransient<IStartupFilter, HostFilteringStartupFilter>(); ???????????????}) ???????????????.UseIISIntegration() ???????????????.UseDefaultServiceProvider((context, options) => ???????????????{ ???????????????????options.ValidateScopes = context.HostingEnvironment.IsDevelopment(); ???????????????}); ???????????return builder; ???????}2.怎么读取配置文件？
我主要提供了2种方式，这里前提是引入Microsoft.AspNetCore.All这个dll，这个里面很多我们需要的东西
从appsettings.json增加配置读取，有两种一个是更改配置以后立即生效，一种是重启以后才生效，具体看下代码:
?//配置如下 ?"JwtSettings": { ???"Issuer": "http://localhost:52588", ???"Audience": "http://localhost:52588", ???"SecretKey": "1235455llllll" ?}, ?"UserSetting": { ???"Name": "wtzzzzz", ???"Age": 12 ?} ?//读取配置 ?????????public void ConfigureServices(IServiceCollection services) ???????{ ???????????services.Configure<CookiePolicyOptions>(options => ???????????{ ???????????????// This lambda determines whether user consent for non-essential cookies is needed for a given request. ???????????????options.CheckConsentNeeded = context => true; ???????????????options.MinimumSameSitePolicy = SameSiteMode.None; ???????????}); ???????????services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_1); ???????????//读取JWT配置文件 ???????????services.Configure<JwtSettingsModel>(Configuration.GetSection("JwtSettings")); ???????????//读取User配置文件 ???????????services.Configure<UserSettingModel>(Configuration.GetSection("UserSetting")); ???????} ??????//controller读取 ?????????????//不支持实时更新 ???????private readonly IOptions<JwtSettingsModel> _jwtConfiguration; ???????//支持实时更新 ???????private readonly IOptionsSnapshot<UserSettingModel> _userConfiguration; ???????public HomeController(IOptions<JwtSettingsModel> jwtConfiguration,IOptionsSnapshot<UserSettingModel> userConfiguration) ???????{ ???????????_jwtConfiguration = jwtConfiguration; ???????????_userConfiguration = userConfiguration; ???????} ???????public IActionResult Index() ???????{ ???????????ViewBag.Issuer = _jwtConfiguration.Value.Issuer; ???????????ViewBag.Name = _userConfiguration.Value.Name; ???????????ViewBag.PersonName =AppConfigurtaionHelper.GetAppSettings<PersonAppSettingModel>("PersonSetting").Area; ???????????return View(); ???????}从外部引入配置文件，这个时候我们要做一件事情，将你新建的配置文件的属性设置为始终复制，至于这个原理是啥我不懂，有大神可以指点下，剩下的具体看代码吧；
{ ?"PersonSetting": { ???"Area": "China" ?}}//外部的工具类 ???public class AppConfigurtaionHelper ???{ ???????public static T GetAppSettings<T>(string key) where T : class, new() ???????{ ???????????IConfiguration config = new ConfigurationBuilder() ???????????.Add(new JsonConfigurationSource { Path = "/Config/setting.json", ReloadOnChange = true }) ???????????.Build(); ???????????var appconfig = new ServiceCollection() ???????????.AddOptions() ???????????.Configure<T>(config.GetSection(key)) ???????????.BuildServiceProvider() ???????????.GetService<IOptions<T>>() ???????????.Value; ???????????return appconfig; ???????} ???}3.Global.asax如何在core中体现；
???????public void Configure(IApplicationBuilder app, IHostingEnvironment env,IApplicationLifetime application) ???????{ ???????????if (env.IsDevelopment()) ???????????{ ???????????????app.UseDeveloperExceptionPage(); ???????????} ???????????else ???????????{ ???????????????app.UseExceptionHandler("/Home/Error"); ???????????????app.UseHsts(); ???????????} ???????????//类似于Application ???????????//开始 ???????????application.ApplicationStarted.Register(() => ???????????{ ???????????????Console.WriteLine("开始了注意"); ???????????}); ???????????//运行中 ???????????application.ApplicationStopping.Register(() => ???????????{ ???????????????Console.WriteLine("运行中"); ???????????}); ???????????//结束 ???????????application.ApplicationStopped.Register(() => ???????????{ ???????????????Console.WriteLine("结束了休息下"); ???????????}); ???????????app.UseHttpsRedirection(); ???????????app.UseStaticFiles(); ???????????app.UseCookiePolicy(); ???????????app.UseMvc(routes => ???????????{ ???????????????routes.MapRoute( ???????????????????name: "default", ???????????????????template: "{controller=Home}/{action=Index}/{id?}"); ???????????}); ???????}IApplicationLifetime这个实现替代在传统应用中Application中生命周期的位置，这个我在上面的代码中已有体现,使用命令的方式运行在控制台就可以看到;
四、DI
针对这个问题,我只能这么说为了为了提高大家,给大家实现一个容器,让大家玩的开心一下,让DI和IOC的思想深入内心,这点有点类似Java操作了,其实早就该这样了,已经让我们变大太懒了,哈哈,借用下蒋神的话,ASP.NET Core的核心是通过一个Server和若干注册的Middleware构成的管道，不论是管道自身的构建，还是Server和Middleware自身的实现，以及构建在这个管道的应用，都需要相应的服务提供支持，ASP.NET Core自身提供了一个DI容器来实现针对服务的注册和消费。换句话说，不只是ASP.NET Core底层框架使用的服务是由这个DI容器来注册和提供，应用级别的服务的注册和提供也需要以来这个DI容器，所以正如本文标题所说的——学习ASP.NET Core，你必须了解无处不在的“依赖注入”。
附上大神的地址:https://www.cnblogs.com/artech/p/dependency-injection-in-asp-net-core.html
不懂DI和IOC的我也附上腾飞大神的地址:https://www.cnblogs.com/jesse2013/p/di-in-aspnetcore.html,
腾飞大神博客里面已经将我想要的说2个问题说的很明白了,我这里还是在稍稍说一下吧。
生命周期问题:
Transient: 每一次GetService都会创建一个新的实例
Scoped：每次Http请求只会产生一个实例;
Singleton：整个应用程序生命周期以内只创建一个实例
这个大神博客里面也有介绍，官方也有介绍，大家可以看下https://docs.microsoft.com/zh-cn/aspnet/core/fundamentals/dependency-injection?view=aspnetcore-2.1
容器的替换:
public IServiceProvider ConfigureServices( ?IServiceCollection services){ ???services.AddMvc(); ???// Add other framework services ????// Add Autofac ???var containerBuilder = new ContainerBuilder(); ???containerBuilder.RegisterModule<DefaultModule>(); ???containerBuilder.Populate(services); ???var container = containerBuilder.Build(); ???return new AutofacServiceProvider(container);}五、MVC
1.Core的请求和MVC的请求有什么不同？
看图说话，主要设计不同主要体现在蒋神说的那句话，Core按照中间件的形式设计，最后全部注入到DI,这个时候我们考虑一个问题,我们想替换任何一个都将变得很容易,但是同样我们又会衍生另外一个问题，当我们服务之间存在依赖的时候，就需要按照顺序进行注入，这个问题需要重视一下，当然微软在设计上也考虑到这点，这里也是简单写个小demo，当你访问网站的时候就会发现网站按照顺序输出来了。MVC还是在IHttpMoudle和IHttpHandle上面做扩展或解耦，整体上本质是不变得，对这块不了解的可以推荐几篇博客给大家看看；推荐大龙龙MVC系列:http://www.cnblogs.com/edisonchou/p/3911558.html
???????????//注册中间件 ???????????app.Use(async (context,next)=> ???????????{ ???????????????await context.Response.WriteAsync("1"); ???????????????await next.Invoke(); ???????????}); ???????????app.Use(next => ???????????{ ???????????????return (context) => ???????????????{ ???????????????????context.Response.WriteAsync("2"); ???????????????????return next(context); ???????????????}; ???????????}); ???????????app.Run(async (context) => ????????????{ ???????????????await context.Response.WriteAsync("3"); ???????????});六、结束
下一篇我们再说，Demo还没时间做好，另外强烈推荐大家去看官方文档：https://docs.microsoft.com/zh-cn/aspnet/core/migration/http-modules?view=aspnetcore-2.1，真的比什么都管用！！！
从明面上学习ASP.NET Core
原文地址：https://www.cnblogs.com/wtzbk/p/9196185.html