ASP.NET Core 01基础知识概述

Program.cs

使用 Web 模板创建的 ASP.NET Core 应用包含 Program.cs 文件中的应用程序启动代码。
Program.cs 文件中包含：

已配置应用所需的服务。
应用的请求处理管道定义为一系列中间件组件。

Program.cs

var builder = WebApplication.CreateBuilder(args);

// Add services to the container.
builder.Services.AddRazorPages();
builder.Services.AddControllersWithViews();

var app = builder.Build();

// Configure the HTTP request pipeline.
if (!app.Environment.IsDevelopment())
{
    app.UseExceptionHandler("/Error");
    app.UseHsts();
}

app.UseHttpsRedirection();
app.UseStaticFiles();

app.UseAuthorization();

app.MapGet("/hi", () => "Hello!");

app.MapDefaultControllerRoute();
app.MapRazorPages();

app.Run();

依赖关系注入（服务）

ASP.NET Core 包含依赖关系注入 (DI)，可在应用中提供配置的服务。使用以上代码中的 WebApplicationBuilder.Services、builder.Services 将服务添加到 DI 容器。实例化 WebApplicationBuilder 时，会添加许多框架提供的服务。在以下代码中，builder 是一个 WebApplicationBuilder：

WebApplicationBuilder

var builder = WebApplication.CreateBuilder(args);

// Add services to the container.
builder.Services.AddRazorPages();
builder.Services.AddControllersWithViews();

var app = builder.Build();

通常使用构造函数注入从 DI 解析服务。 DI 框架在运行时提供此服务的实例。

构造函数注入从 DI 解析服务

public class IndexModel : PageModel
{
    private readonly RazorPagesMovieContext _context;
    private readonly ILogger<IndexModel> _logger;

    public IndexModel(RazorPagesMovieContext context, ILogger<IndexModel> logger)
    {
        _context = context;
        _logger = logger;
    }

    public IList<Movie> Movie { get;set; }

    public async Task OnGetAsync()
    {
        _logger.LogInformation("IndexModel OnGetAsync.");
        Movie = await _context.Movie.ToListAsync();
    }
}

中间件

请求处理管道由一系列中间件组件组成。每个组件在 HttpContext 上执行操作，调用管道中的下一个中间件或终止请求。
按照惯例，通过调用 Use{Feature} 扩展方法，向管道添加中间件组件。

中间件

// Configure the HTTP request pipeline.
if (!app.Environment.IsDevelopment())
{
    app.UseExceptionHandler("/Error");
    app.UseHsts();
}

app.UseHttpsRedirection();
app.UseStaticFiles();

app.UseAuthorization();

主机

ASP.NET Core 应用在启动时构建主机。主机封装应用的所有资源，例如：

HTTP 服务器实现

中间件组件
Logging
依赖关系注入 (DI) 服务
Configuration

有三个不同的主机：

.NET WebApplication 主机，也称为最小主机。
.NET 通用主机
ASP.NET Core Web 主机

建议使用 .NET WebApplication 主机，并在所有 ASP.NET Core 模板中使用。 .NET WebApplication 主机和 .NET 通用主机共享许多相同的接口和类。 ASP.NET Core Web 主机仅用于支持后向兼容性。

WebApplication 主机实例化

var builder = WebApplication.CreateBuilder(args);

// Add services to the container.
builder.Services.AddRazorPages();
builder.Services.AddControllersWithViews();

var app = builder.Build();//实例化

WebApplicationBuilder.Build 方法使用一组默认选项配置主机，例如：

将 Kestrel 用作 Web 服务器并启用 IIS 集成。
从 appsettings.json、环境变量、命令行参数和其他配置源中加载配置。
将日志记录输出发送到控制台并调试提供程序。

服务器

ASP.NET Core 应用使用 HTTP 服务器实现侦听 HTTP 请求。服务器对应用的请求在表面上呈现为一组由 HttpContext 组成的请求功能。

Windows

ASP.NET Core 提供以下服务器实现：

Kestrel 是跨平台 Web 服务器。 Kestrel 通常使用 IIS 在反向代理配置中运行。在 ASP.NET Core 2.0 或更高版本中，Kestrel 可作为面向公众的边缘服务器运行，直接向 Internet 公开。
IIS HTTP 服务器适用于使用 IIS 的 Windows。借助此服务器，ASP.NET Core 应用和 IIS 在同一进程中运行。
HTTP.sys是适用于不与 IIS 一起使用的 Windows 的服务器。

Linux

ASP.NET Core 提供 Kestrel 跨平台服务器实现。在 ASP.NET Core 2.0 或更高版本中，Kestrel 可作为面向公众的边缘服务器运行，直接向 Internet 公开。 Kestrel 通常使用 Nginx 或 Apache 在反向代理配置中运行。

配置

ASP.NET Core 提供了配置框架，可以从配置提供程序的有序集中将设置作为名称/值对。可将内置配置提供程序用于各种源，例如 .json 文件、.xml 文件、环境变量和命令行参数。可编写自定义配置提供程序以支持其他源。

默认情况下，ASP.NET Core 应用配置为从 appsettings.json、环境变量和命令行等读取内容。加载应用配置后，来自环境变量的值将替代来自 appsettings.json 的值。

环境

执行环境（例如 Development、Staging 和 Production）在 ASP.NET Core 中可用。通过设置 ASPNETCORE_ENVIRONMENT 环境变量来指定应用的运行环境。 ASP.NET Core 在应用启动时读取该环境变量，并将该值存储在 IWebHostEnvironment 实现中。通过依赖关系注入 (DI)，可以在应用中任何位置实现此操作。

app.Environment.IsDevelopment()

Logging

ASP.NET Core 支持适用于各种内置和第三方日志记录提供程序的日志记录 API。可用的提供程序包括：

控制台
调试
Windows 事件跟踪
Windows 事件日志
TraceSource
Azure 应用服务
Azure Application Insights

若要创建服务，请从依赖关系注入 (DI) 解析 ILogger 服务，并调用 LogInformation 等日志记录方法。

日志

public class IndexModel : PageModel
{
    private readonly RazorPagesMovieContext _context;
    private readonly ILogger<IndexModel> _logger;

    public IndexModel(RazorPagesMovieContext context, ILogger<IndexModel> logger)
    {
        _context = context;
        _logger = logger;
    }

    public IList<Movie> Movie { get;set; }

    public async Task OnGetAsync()
    {
        _logger.LogInformation("IndexModel OnGetAsync.");
        Movie = await _context.Movie.ToListAsync();
    }
}

路由

路由是映射到处理程序的 URL 模式。处理程序通常是 Razor 页面、MVC 控制器中的操作方法或中间件。借助 ASP.NET Core 路由，可以控制应用使用的 URL。

以下由 ASP.NET Core Web 应用程序模板生成的代码调用 UseRouting：

app.UseRouting();

错误处理

ASP.NET Core 具有用于处理错误的内置功能，例如：

开发人员异常页
自定义错误页
静态状态代码页
启动异常处理

发出 HTTP 请求

IHttpClientFactory 的实现可用于创建 HttpClient 实例。工厂可以：

提供一个中心位置，用于命名和配置逻辑 HttpClient 实例。例如，注册并配置 github 客户端以访问 GitHub。注册并配置默认客户端以实现其他目的。
支持多个委托处理程序的注册和链接，以生成出站请求中间件管道。此模式类似于 ASP.NET Core 的入站中间件管道。此模式提供了一种用于管理 HTTP 请求相关问题的机制，包括缓存、错误处理、序列化以及日志记录。
与 Polly 集成，这是用于瞬时故障处理的常用第三方库。
管理基础 HttpClientHandler 实例的池和生存期，避免手动管理 HttpClient 生存期时可能出现的常见 DNS 问题。
通过 ILogger 添加可配置的日志记录体验，用于记录通过工厂创建的客户端发送的所有请求。

内容根

内容根目录是指向以下内容的基路径：

托管应用的可执行文件 (.exe)。
构成应用程序的已编译程序集 (.dll)。
应用使用的内容文件，例如：Razor 文件（.cshtml、.razor）、配置文件（.json、.xml）、数据文件 (.db)
Web 根目录，通常是 wwwroot 文件夹。

Web 根

Web 根目录是公用静态资源文件的基路径，例如：

样式表 (.css)
JavaScript (.js)
图像（.png、.jpg）

默认情况下，静态文件仅从 Web 根目录及其子目录提供。 Web 根目录路径默认为 {content root}/wwwroot。在构建主机时设置路径，可指定不同的 Web 根目录。

在 Razor.cshtml 文件中，~/ 指向 Web 根。以 ~/ 开头的路径称为虚拟路径。

WebApplicationBuilder 源代码

// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.

using System.Diagnostics;
using System.Linq;
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using Microsoft.Extensions.Logging;

namespace Microsoft.AspNetCore.Builder
{
    /// <summary>
    /// A builder for web applications and services.
    /// </summary>
    public sealed class WebApplicationBuilder
    {
        private const string EndpointRouteBuilderKey = "__EndpointRouteBuilder";

        private readonly HostBuilder _hostBuilder = new();
        private readonly BootstrapHostBuilder _bootstrapHostBuilder;
        private readonly WebApplicationServiceCollection _services = new();
        private readonly List<KeyValuePair<string, string>> _hostConfigurationValues;

        private WebApplication? _builtApplication;

        internal WebApplicationBuilder(WebApplicationOptions options, Action<IHostBuilder>? configureDefaults = null)
        {
            Services = _services;

            var args = options.Args;

            // Run methods to configure both generic and web host defaults early to populate config from appsettings.json
            // environment variables (both DOTNET_ and ASPNETCORE_ prefixed) and other possible default sources to prepopulate
            // the correct defaults.
            _bootstrapHostBuilder = new BootstrapHostBuilder(Services, _hostBuilder.Properties);

            // Don't specify the args here since we want to apply them later so that args
            // can override the defaults specified by ConfigureWebHostDefaults
            _bootstrapHostBuilder.ConfigureDefaults(args: null);

            // This is for testing purposes
            configureDefaults?.Invoke(_bootstrapHostBuilder);

            // We specify the command line here last since we skipped the one in the call to ConfigureDefaults.
            // The args can contain both host and application settings so we want to make sure
            // we order those configuration providers appropriately without duplicating them
            if (args is { Length: > 0 })
            {
                _bootstrapHostBuilder.ConfigureAppConfiguration(config =>
                {
                    config.AddCommandLine(args);
                });
            }

            _bootstrapHostBuilder.ConfigureWebHostDefaults(webHostBuilder =>
            {
                // Runs inline.
                webHostBuilder.Configure(ConfigureApplication);

                // Attempt to set the application name from options
                options.ApplyApplicationName(webHostBuilder);
            });

            // Apply the args to host configuration last since ConfigureWebHostDefaults overrides a host specific setting (the application name).
            _bootstrapHostBuilder.ConfigureHostConfiguration(config =>
            {
                if (args is { Length: > 0 })
                {
                    config.AddCommandLine(args);
                }

                // Apply the options after the args
                options.ApplyHostConfiguration(config);
            });

            Configuration = new();

            // Collect the hosted services separately since we want those to run after the user's hosted services
            _services.TrackHostedServices = true;

            // This is the application configuration
            var (hostContext, hostConfiguration) = _bootstrapHostBuilder.RunDefaultCallbacks(Configuration, _hostBuilder);

            // Stop tracking here
            _services.TrackHostedServices = false;

            // Capture the host configuration values here. We capture the values so that
            // changes to the host configuration have no effect on the final application. The
            // host configuration is immutable at this point.
            _hostConfigurationValues = new(hostConfiguration.AsEnumerable());

            // Grab the WebHostBuilderContext from the property bag to use in the ConfigureWebHostBuilder
            var webHostContext = (WebHostBuilderContext)hostContext.Properties[typeof(WebHostBuilderContext)];

            // Grab the IWebHostEnvironment from the webHostContext. This also matches the instance in the IServiceCollection.
            Environment = webHostContext.HostingEnvironment;
            Logging = new LoggingBuilder(Services);
            Host = new ConfigureHostBuilder(hostContext, Configuration, Services);
            WebHost = new ConfigureWebHostBuilder(webHostContext, Configuration, Services);

            Services.AddSingleton<IConfiguration>(_ => Configuration);
        }

        /// <summary>
        /// Provides information about the web hosting environment an application is running.
        /// </summary>
        public IWebHostEnvironment Environment { get; }

        /// <summary>
        /// A collection of services for the application to compose. This is useful for adding user provided or framework provided services.
        /// </summary>
        public IServiceCollection Services { get; }

        /// <summary>
        /// A collection of configuration providers for the application to compose. This is useful for adding new configuration sources and providers.
        /// </summary>
        public ConfigurationManager Configuration { get; }

        /// <summary>
        /// A collection of logging providers for the application to compose. This is useful for adding new logging providers.
        /// </summary>
        public ILoggingBuilder Logging { get; }

        /// <summary>
        /// An <see cref="IWebHostBuilder"/> for configuring server specific properties, but not building.
        /// To build after configuration, call <see cref="Build"/>.
        /// </summary>
        public ConfigureWebHostBuilder WebHost { get; }

        /// <summary>
        /// An <see cref="IHostBuilder"/> for configuring host specific properties, but not building.
        /// To build after configuration, call <see cref="Build"/>.
        /// </summary>
        public ConfigureHostBuilder Host { get; }

        /// <summary>
        /// Builds the <see cref="WebApplication"/>.
        /// </summary>
        /// <returns>A configured <see cref="WebApplication"/>.</returns>
        public WebApplication Build()
        {
            // Wire up the host configuration here. We don't try to preserve the configuration
            // source itself here since we don't support mutating the host values after creating the builder.
            _hostBuilder.ConfigureHostConfiguration(builder =>
            {
                builder.AddInMemoryCollection(_hostConfigurationValues);
            });

            var chainedConfigSource = new TrackingChainedConfigurationSource(Configuration);

            // Wire up the application configuration by copying the already built configuration providers over to final configuration builder.
            // We wrap the existing provider in a configuration source to avoid re-bulding the already added configuration sources.
            _hostBuilder.ConfigureAppConfiguration(builder =>
            {
                builder.Add(chainedConfigSource);

                foreach (var (key, value) in ((IConfigurationBuilder)Configuration).Properties)
                {
                    builder.Properties[key] = value;
                }
            });

            // This needs to go here to avoid adding the IHostedService that boots the server twice (the GenericWebHostService).
            // Copy the services that were added via WebApplicationBuilder.Services into the final IServiceCollection
            _hostBuilder.ConfigureServices((context, services) =>
            {
                // We've only added services configured by the GenericWebHostBuilder and WebHost.ConfigureWebDefaults
                // at this point. HostBuilder news up a new ServiceCollection in HostBuilder.Build() we haven't seen
                // until now, so we cannot clear these services even though some are redundant because
                // we called ConfigureWebHostDefaults on both the _deferredHostBuilder and _hostBuilder.
                foreach (var s in _services)
                {
                    services.Add(s);
                }

                // Add the hosted services that were initially added last
                // this makes sure any hosted services that are added run after the initial set
                // of hosted services. This means hosted services run before the web host starts.
                foreach (var s in _services.HostedServices)
                {
                    services.Add(s);
                }

                // Clear the hosted services list out
                _services.HostedServices.Clear();

                // Add any services to the user visible service collection so that they are observable
                // just in case users capture the Services property. Orchard does this to get a "blueprint"
                // of the service collection

                // Drop the reference to the existing collection and set the inner collection
                // to the new one. This allows code that has references to the service collection to still function.
                _services.InnerCollection = services;

                var hostBuilderProviders = ((IConfigurationRoot)context.Configuration).Providers;

                if (!hostBuilderProviders.Contains(chainedConfigSource.BuiltProvider))
                {
                    // Something removed the _hostBuilder's TrackingChainedConfigurationSource pointing back to the ConfigurationManager.
                    // This is likely a test using WebApplicationFactory. Replicate the effect by clearing the ConfingurationManager sources.
                    ((IConfigurationBuilder)Configuration).Sources.Clear();
                }

                // Make builder.Configuration match the final configuration. To do that, we add the additional
                // providers in the inner _hostBuilders's Configuration to the ConfigurationManager.
                foreach (var provider in hostBuilderProviders)
                {
                    if (!ReferenceEquals(provider, chainedConfigSource.BuiltProvider))
                    {
                        ((IConfigurationBuilder)Configuration).Add(new ConfigurationProviderSource(provider));
                    }
                }
            });

            // Run the other callbacks on the final host builder
            Host.RunDeferredCallbacks(_hostBuilder);

            _builtApplication = new WebApplication(_hostBuilder.Build());

            // Mark the service collection as read-only to prevent future modifications
            _services.IsReadOnly = true;

            // Resolve both the _hostBuilder's Configuration and builder.Configuration to mark both as resolved within the
            // service provider ensuring both will be properly disposed with the provider.
            _ = _builtApplication.Services.GetService<IEnumerable<IConfiguration>>();

            return _builtApplication;
        }

        private void ConfigureApplication(WebHostBuilderContext context, IApplicationBuilder app)
        {
            Debug.Assert(_builtApplication is not null);

            // UseRouting called before WebApplication such as in a StartupFilter
            // lets remove the property and reset it at the end so we don't mess with the routes in the filter
            if (app.Properties.TryGetValue(EndpointRouteBuilderKey, out var priorRouteBuilder))
            {
                app.Properties.Remove(EndpointRouteBuilderKey);
            }

            if (context.HostingEnvironment.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
            }

            // Wrap the entire destination pipeline in UseRouting() and UseEndpoints(), essentially:
            // destination.UseRouting()
            // destination.Run(source)
            // destination.UseEndpoints()

            // Set the route builder so that UseRouting will use the WebApplication as the IEndpointRouteBuilder for route matching
            app.Properties.Add(WebApplication.GlobalEndpointRouteBuilderKey, _builtApplication);

            // Only call UseRouting() if there are endpoints configured and UseRouting() wasn't called on the global route builder already
            if (_builtApplication.DataSources.Count > 0)
            {
                // If this is set, someone called UseRouting() when a global route builder was already set
                if (!_builtApplication.Properties.TryGetValue(EndpointRouteBuilderKey, out var localRouteBuilder))
                {
                    app.UseRouting();
                }
                else
                {
                    // UseEndpoints will be looking for the RouteBuilder so make sure it's set
                    app.Properties[EndpointRouteBuilderKey] = localRouteBuilder;
                }
            }

            // Wire the source pipeline to run in the destination pipeline
            app.Use(next =>
            {
                _builtApplication.Run(next);
                return _builtApplication.BuildRequestDelegate();
            });

            if (_builtApplication.DataSources.Count > 0)
            {
                // We don't know if user code called UseEndpoints(), so we will call it just in case, UseEndpoints() will ignore duplicate DataSources
                app.UseEndpoints(_ => { });
            }

            // Copy the properties to the destination app builder
            foreach (var item in _builtApplication.Properties)
            {
                app.Properties[item.Key] = item.Value;
            }

            // Remove the route builder to clean up the properties, we're done adding routes to the pipeline
            app.Properties.Remove(WebApplication.GlobalEndpointRouteBuilderKey);

            // reset route builder if it existed, this is needed for StartupFilters
            if (priorRouteBuilder is not null)
            {
                app.Properties[EndpointRouteBuilderKey] = priorRouteBuilder;
            }
        }

        private sealed class LoggingBuilder : ILoggingBuilder
        {
            public LoggingBuilder(IServiceCollection services)
            {
                Services = services;
            }

            public IServiceCollection Services { get; }
        }
    }
}

posted @ 2022-09-06 15:04 BLJCharles 阅读(104) 评论(0) 编辑收藏举报

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ASP.NET Core 01基础知识概述

Program.cs

依赖关系注入（服务）

中间件

主机

服务器

Windows

Linux

配置

环境

Logging

路由

错误处理

发出 HTTP 请求

内容根

Web 根

WebApplicationBuilder 源代码

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