WebHostBuilder の変更点

• 追加された行はこの色です。
• 削除された行はこの色です。
• +.NetCore+WebHostBuilder へ行く。
• +.NetCore+WebHostBuilder の差分を削除

#author("2023-11-19T11:33:31+08:00","default:Admin","Admin")
#author("2023-11-19T11:35:26+08:00","default:Admin","Admin")
[[ASP.NET Core Web]]

&color(red){※This article is based on .NET 7};

#contents

* 概要 [#m8048734]

WebHostBuilder的使命非常明确：就是创建作为应用宿主的WebHost。

由于在创建WebHost的时候需要提供注册的服务器和由所有注册中间件构建而成的RequestDelegate，所以在对应接口IWebHostBuilder中，为它定义了三个核心方法。


#codeprettify{{
public interface IWebHostBuilder
{
    IWebHostBuilder UseServer(IServer server);
    IWebHostBuilder Configure(Action<IApplicationBuilder> configure);
    IWebHost Build();
}
}}

除了用来创建WebHost的Build方法之外，我们提供了用来注册服务器的UseServer方法和用来注册中间件的Configure方法。Configure方法提供了一个类型为Action<IApplicationBuilder>的参数，意味着我们针对中间件的注册是利用上面介绍的IApplicationBuilder对象来完成的。



如下所示的WebHostBuilder是针对IWebHostBuilder接口的默认实现，它具有两个字段分别用来保存注册的中间件和调用Configure方法提供的Action<IApplicationBuilder>对象。当Build方法被调用之后，我们创建一个ApplicationBuilder对象，并将它作为参数调用这些Action<IApplicationBuilder>委托，进而将所有中间件全部注册到这个ApplicationBuilder对象上。我们最终调用它的Build方法得到由所有中间件共同构建的RequestDelegate对象，并利用它和注册的服务器构建作为应用宿主的WebHost对象。


#codeprettify{{
public class WebHostBuilder : IWebHostBuilder
{
    private IServer _server;
    private readonly List<Action<IApplicationBuilder>> _configures = new List<Action<IApplicationBuilder>>();   
    public IWebHostBuilder Configure(Action<IApplicationBuilder> configure)
    {
        _configures.Add(configure);
        return this;
    }
    public IWebHostBuilder UseServer(IServer server)
    {
        _server = server;
        return this;
    }   
    public IWebHost Build()
    {
        var builder = new ApplicationBuilder();
        foreach (var configure in _configures)
        {
            configure(builder);
        }
        return new WebHost(_server, builder.Build());
    }
}
}}

* 默认提供的做法 [#x6004e41]

创建IWebHostBuilder

Program.cs
#codeprettify{{
namespace WebApplication1
{
    public class Program
    {
        public static void Main(string[] args)
        {
            CreateHostBuilder(args).Build().Run();
        }

        public static IHostBuilder CreateHostBuilder(string[] args) =>
            Host.CreateDefaultBuilder(args)
                .ConfigureWebHostDefaults(webBuilder =>
                {
                    //指定Startup类型，返回一个IWebHostBuilder
                    webBuilder.UseStartup<Startup>();
                });
    }
}
}}

Startup.cs

#codeprettify{{
namespace WebApplication1
{
    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();
            services.AddSwaggerGen(c =>
            {
                c.SwaggerDoc("v1", new OpenApiInfo { Title = "WebApplication1", Version = "v1" });
            });
        }

        // 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.UseSwagger();
                app.UseSwaggerUI(c => c.SwaggerEndpoint("/swagger/v1/swagger.json", "WebApplication1 v1"));
            }

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

* 定制IHostBuilder [#k64de5c3]

在.Net6之前的IHostBuilder扩展方法现在可以通过属性Host来使用：

#codeprettify{{
var builder = WebApplication.CreateBuilder(args);

// Wait 30 seconds for graceful shutdown
builder.Host.ConfigureHostOptions(o => o.ShutdownTimeout = TimeSpan.FromSeconds(30));

var app = builder.Build()
}}

* 定义IWebHostBuilder [#n628e48e]
#codeprettify{{
在.Net6之前的IWebHostBuilder扩展方法可以在属性WebHost上使用:

var builder = WebApplication.CreateBuilder(args);

// Change the HTTP server implemenation to be HTTP.sys based
builder.WebHost.UseHttpSys();

var app = builder.Build();
}}


#hr();
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