本章将和大家分享ASP.NET Core中的配置Configuration的使用及其源码解析。
1、使用 IConfiguration 读取配置文件内容
Demo的目录结构如下所示：
本Demo的Web项目为ASP.NET Core Web 应用程序（目标框架为.NET Core 3.1） MVC项目。
首先添加配置文件，内容如下所示：（注意：配置文件的编码必须调整为UTF-8）
appsettings.Development.json 内容如下：
{
"Logging": {
"LogLevel": {
"Default": "Information",
"Microsoft": "Warning",
"Microsoft.Hosting.Lifetime": "Information"
}
}
}
appsettings.json 内容如下：
{
"Logging": {
"LogLevel": {
"Default": "Information",
"Microsoft": "Warning",
"Microsoft.Hosting.Lifetime": "Information"
}
},
"AllowedHosts": "*"
}
hostsettings.json 内容如下：
{
"urls": "http://*:8001"
}
otherconfig.json 内容如下：
{
"OtherConfig": {
"accountkey": "accountkey_测试",
"accountsecret": "accountsecret_测试"
}
}
otherconfig.Production.json 内容如下：
{
"OtherConfig": {
"accountkey": "accountkey_正式",
"accountsecret": "accountsecret_正式"
}
}
siteconfig.json 内容如下：
{
"ConnectionStrings": "server=127.0.0.1;port=3306;database=dotnetcore;uid=root;pwd=123456;CharSet=utf8;",
"SiteConfig": {
"Name": "测试站点名称",
"Admin": "http://admin.demo.test",
"Api": "http://api.demo.test",
"Image": "http://image.demo.test",
"My": "http://my.demo.test",
"Upload": "http://upload.demo.test",
"Www": "http://www.demo.test",
"Domain": {
"mc_1633_com": "http://192.168.18.209:8000/mc"
}
}
}
siteconfig.Production.json 内容如下：
{
"ConnectionStrings": "server=127.0.0.1;port=3306;database=dotnetcore;uid=root;pwd=123456;CharSet=utf8;",
"SiteConfig": {
"Name": "正式站点名称",
"Admin": "http://admin.demo.com",
"Api": "http://api.demo.com",
"Image": "http://image.demo.com",
"My": "http://my.demo.com",
"Upload": "http://upload.demo.com",
"Www": "http://www.demo.com"
}
}
接着修改 Program.cs 类，如下所示：
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.Hosting;
using Microsoft.Extensions.Logging;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
namespace IConfiguration_IOptions_Demo
{
public class Program
{
public static void Main(string[] args)
{
//CreateHostBuilder(args).Build().Run();
var hostBuilder = CreateHostBuilder(args);
hostBuilder.Build().Run();
}
public static IHostBuilder CreateHostBuilder(string[] args) =>
Host.CreateDefaultBuilder(args)
.ConfigureAppConfiguration((hostingContext, config) =>
{
var env = hostingContext.HostingEnvironment;
var basePath = System.IO.Path.Combine(env.ContentRootPath, "ConfigFiles");
config.SetBasePath(basePath: basePath)
.AddJsonFile(path: "hostsettings.json", optional: true, reloadOnChange: true)
.AddJsonFile(path: $"hostsettings.{env.EnvironmentName}.json", optional: true, reloadOnChange: true)
.AddJsonFile(path: "otherconfig.json", optional: true, reloadOnChange: true)
.AddJsonFile(path: $"otherconfig.{env.EnvironmentName}.json", optional: true, reloadOnChange: true)
.AddJsonFile(path: "siteconfig.json", optional: true, reloadOnChange: true)
.AddJsonFile(path: $"siteconfig.{env.EnvironmentName}.json", optional: true, reloadOnChange: true);
config.AddEnvironmentVariables();
})
.ConfigureWebHostDefaults(webBuilder =>
{
webBuilder.UseStartup<Startup>();
});
}
}
最后使用 IConfiguration 读取配置文件内容，如下所示：
using Microsoft.AspNetCore.Mvc;
using Microsoft.Extensions.Configuration;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace IConfiguration_IOptions_Demo.Controllers
{
public class ConfigurationDemoController : Controller
{
private readonly IConfiguration _configuration;
/// <summary>
/// 构造函数
/// </summary>
public ConfigurationDemoController(IConfiguration configuration)
{
_configuration = configuration;
}
/// <summary>
/// IConfiguration的使用
/// </summary>
/// <returns></returns>
public IActionResult Index()
{
var sb = new StringBuilder();
sb.AppendLine($"_configuration[\"Logging:LogLevel:Default\"] => {_configuration["Logging:LogLevel:Default"]}");
sb.AppendLine($"_configuration[\"AllowedHosts\"] => {_configuration["AllowedHosts"]}");
sb.AppendLine($"_configuration[\"SiteConfig:Name\"] => {_configuration["SiteConfig:Name"]}");
sb.AppendLine($"_configuration[\"OtherConfig:accountkey\"] => {_configuration["OtherConfig:accountkey"]}");
IConfigurationSection siteConfigSection = _configuration.GetSection("SiteConfig");
sb.AppendLine($"siteConfigSection[\"Name\"] => {siteConfigSection["Name"]}");
sb.AppendLine($"siteConfigSection[\"Domain:mc_1633_com\"] => {siteConfigSection["Domain:mc_1633_com"]}");
IConfigurationSection domainSection = _configuration.GetSection("SiteConfig").GetSection("Domain");
sb.AppendLine($"domainSection[\"mc_1633_com\"] => {domainSection["mc_1633_com"]}");
return Content(sb.ToString());
}
}
}
访问 /ConfigurationDemo/Index 运行结果如下：
2、IConfiguration 源码解析
首先我们通过调试来看下注入给IConfiguration的到底是什么？
可以看出它是 Microsoft.Extensions.Configuration.ConfigurationRoot 类的实例。
我们接着往下调试看下 _configuration.GetSection("SiteConfig") 返回的是啥？
可以看出它返回的是 Microsoft.Extensions.Configuration.ConfigurationSection 类的实例。
其实 ConfigurationRoot 类实现了 IConfigurationRoot 接口，而 IConfigurationRoot 接口又实现了 IConfiguration 接口，并且 ConfigurationSection 类实现了 IConfigurationSection 接口，而 IConfigurationSection 接口又实现了 IConfiguration 接口。IConfiguration、IConfigurationRoot 和 IConfigurationSection 它们三者之间的关系如下：
讲到这里，大家对配置的获取，应该有了一个基本的认识。 那么下面我们就通过查看源码的方式来理解它的底层实现逻辑。
我们从 Program.cs 类的 Main(string[] args) 主函数（应用程序的入口）开始查找：
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.Hosting;
using Microsoft.Extensions.Logging;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
namespace IConfiguration_IOptions_Demo
{
public class Program
{
public static void Main(string[] args)
{
//CreateHostBuilder(args).Build().Run();
var hostBuilder = CreateHostBuilder(args);
hostBuilder.Build().Run();
}
public static IHostBuilder CreateHostBuilder(string[] args) =>
Host.CreateDefaultBuilder(args)
.ConfigureAppConfiguration((hostingContext, config) =>
{
var env = hostingContext.HostingEnvironment;
var basePath = System.IO.Path.Combine(env.ContentRootPath, "ConfigFiles");
config.SetBasePath(basePath: basePath)
.AddJsonFile(path: "hostsettings.json", optional: true, reloadOnChange: true)
.AddJsonFile(path: $"hostsettings.{env.EnvironmentName}.json", optional: true, reloadOnChange: true)
.AddJsonFile(path: "otherconfig.json", optional: true, reloadOnChange: true)
.AddJsonFile(path: $"otherconfig.{env.EnvironmentName}.json", optional: true, reloadOnChange: true)
.AddJsonFile(path: "siteconfig.json", optional: true, reloadOnChange: true)
.AddJsonFile(path: $"siteconfig.{env.EnvironmentName}.json", optional: true, reloadOnChange: true);
config.AddEnvironmentVariables();
})
.ConfigureWebHostDefaults(webBuilder =>
{
webBuilder.UseStartup<Startup>();
});
}
}
首先找到 Host 类，源码如下：
// Copyright (c) .NET Foundation. All rights reserved.
// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
using System.IO;
using System.Reflection;
using System.Runtime.InteropServices;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.Logging;
using Microsoft.Extensions.Logging.EventLog;
namespace Microsoft.Extensions.Hosting
{
/// <summary>
/// Provides convenience methods for creating instances of <see cref="IHostBuilder"/> with pre-configured defaults.
/// </summary>
public static class Host
{
/// <summary>
/// Initializes a new instance of the <see cref="HostBuilder"/> class with pre-configured defaults.
/// </summary>
/// <remarks>
/// The following defaults are applied to the returned <see cref="HostBuilder"/>:
/// <list type="bullet">
/// <item><description>set the <see cref="IHostEnvironment.ContentRootPath"/> to the result of <see cref="Directory.GetCurrentDirectory()"/></description></item>
/// <item><description>load host <see cref="IConfiguration"/> from "DOTNET_" prefixed environment variables</description></item>
/// <item><description>load app <see cref="IConfiguration"/> from 'appsettings.json' and 'appsettings.[<see cref="IHostEnvironment.EnvironmentName"/>].json'</description></item>
/// <item><description>load app <see cref="IConfiguration"/> from User Secrets when <see cref="IHostEnvironment.EnvironmentName"/> is 'Development' using the entry assembly</description></item>
/// <item><description>load app <see cref="IConfiguration"/> from environment variables</description></item>
/// <item><description>configure the <see cref="ILoggerFactory"/> to log to the console, debug, and event source output</description></item>
/// <item><description>enables scope validation on the dependency injection container when <see cref="IHostEnvironment.EnvironmentName"/> is 'Development'</description></item>
/// </list>
/// </remarks>
/// <returns>The initialized <see cref="IHostBuilder"/>.</returns>
public static IHostBuilder CreateDefaultBuilder() =>
CreateDefaultBuilder(args: null);
/// <summary>
/// Initializes a new instance of the <see cref="HostBuilder"/> class with pre-configured defaults.
/// </summary>
/// <remarks>
/// The following defaults are applied to the returned <see cref="HostBuilder"/>:
/// <list type="bullet">
/// <item><description>set the <see cref="IHostEnvironment.ContentRootPath"/> to the result of <see cref="Directory.GetCurrentDirectory()"/></description></item>
/// <item><description>load host <see cref="IConfiguration"/> from "DOTNET_" prefixed environment variables</description></item>
/// <item><description>load host <see cref="IConfiguration"/> from supplied command line args</description></item>
/// <item><description>load app <see cref="IConfiguration"/> from 'appsettings.json' and 'appsettings.[<see cref="IHostEnvironment.EnvironmentName"/>].json'</description></item>
/// <item><description>load app <see cref="IConfiguration"/> from User Secrets when <see cref="IHostEnvironment.EnvironmentName"/> is 'Development' using the entry assembly</description></item>
/// <item><description>load app <see cref="IConfiguration"/> from environment variables</description></item>
/// <item><description>load app <see cref="IConfiguration"/> from supplied command line args</description></item>
/// <item><description>configure the <see cref="ILoggerFactory"/> to log to the console, debug, and event source output</description></item>
/// <item><description>enables scope validation on the dependency injection container when <see cref="IHostEnvironment.EnvironmentName"/> is 'Development'</description></item>
/// </list>
/// </remarks>
/// <param name="args">The command line args.</param>
/// <returns>The initialized <see cref="IHostBuilder"/>.</returns>
public static IHostBuilder CreateDefaultBuilder(string[] args)
{
var builder = new HostBuilder();
builder.UseContentRoot(Directory.GetCurrentDirectory());
builder.ConfigureHostConfiguration(config =>
{
config.AddEnvironmentVariables(prefix: "DOTNET_");
if (args != null)
{
config.AddCommandLine(args);
}
});
builder.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() && !string.IsNullOrEmpty(env.ApplicationName))
{
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) =>
{
var isWindows = RuntimeInformation.IsOSPlatform(OSPlatform.Windows);
// IMPORTANT: This needs to be added *before* configuration is loaded, this lets
// the defaults be overridden by the configuration.
if (isWindows)
{
// Default the EventLogLoggerProvider to warning or above
logging.AddFilter<EventLogLoggerProvider>(level => level >= LogLevel.Warning);
}
logging.AddConfiguration(hostingContext.Configuration.GetSection("Logging"));
logging.AddConsole();
logging.AddDebug();
logging.AddEventSourceLogger();
if (isWindows)
{
// Add the EventLogLoggerProvider on windows machines
logging.AddEventLog();
}
})
.UseDefaultServiceProvider((context, options) =>
{
var isDevelopment = context.HostingEnvironment.IsDevelopment();
options.ValidateScopes = isDevelopment;
options.ValidateOnBuild = isDevelopment;
});
return builder;
}
}
}
从该类可以看出调用Host.CreateDefaultBuilder(args)这个方法最终返回的是HostBuilder类型的对象，且在Main(string[] args)主函数中最终会调用该对象的Build()方法。
此外还可以看出 Host.CreateDefaultBuilder(args) 这个方法的内部默认就已经添加了appsettings.json的这个配置，这也就解释了为什么在Program.cs类中添加配置文件的时候不需要加appsettings.json的原因。
接下来我们就来看一下 builder.ConfigureAppConfiguration(...) 这个方法内部到底做了什么操作，我们找到 HostBuilder 类的源码，如下：
// Copyright (c) .NET Foundation. All rights reserved.
// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
using System;
using System.Collections.Generic;
using System.IO;
using System.Reflection;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.FileProviders;
using Microsoft.Extensions.Hosting.Internal;
namespace Microsoft.Extensions.Hosting
{
/// <summary>
/// A program initialization utility.
/// </summary>
public class HostBuilder : IHostBuilder
{
private List<Action<IConfigurationBuilder>> _configureHostConfigActions = new List<Action<IConfigurationBuilder>>();
private List<Action<HostBuilderContext, IConfigurationBuilder>> _configureAppConfigActions = new List<Action<HostBuilderContext, IConfigurationBuilder>>();
private List<Action<HostBuilderContext, IServiceCollection>> _configureServicesActions = new List<Action<HostBuilderContext, IServiceCollection>>();
private List<IConfigureContainerAdapter> _configureContainerActions = new List<IConfigureContainerAdapter>();
private IServiceFactoryAdapter _serviceProviderFactory = new ServiceFactoryAdapter<IServiceCollection>(new DefaultServiceProviderFactory());
private bool _hostBuilt;
private IConfiguration _hostConfiguration;
private IConfiguration _appConfiguration;
private HostBuilderContext _hostBuilderContext;
private HostingEnvironment _hostingEnvironment;
private IServiceProvider _appServices;
/// <summary>
/// A central location for sharing state between components during the host building process.
/// </summary>
public IDictionary<object, object> Properties { get; } = new Dictionary<object, object>();
/// <summary>
/// Set up the configuration for the builder itself. This will be used to initialize the <see cref="IHostEnvironment"/>
/// for use later in the build process. This can be called multiple times and the results will be additive.
/// </summary>
/// <param name="configureDelegate">The delegate for configuring the <see cref="IConfigurationBuilder"/> that will be used
/// to construct the <see cref="IConfiguration"/> for the host.</param>
/// <returns>The same instance of the <see cref="IHostBuilder"/> for chaining.</returns>
public IHostBuilder ConfigureHostConfiguration(Action<IConfigurationBuilder> configureDelegate)
{
_configureHostConfigActions.Add(configureDelegate ?? throw new ArgumentNullException(nameof(configureDelegate)));
return this;
}
/// <summary>
/// Sets up the configuration for the remainder of the build process and application. This can be called multiple times and
/// the results will be additive. The results will be available at <see cref="HostBuilderContext.Configuration"/> for
/// subsequent operations, as well as in <see cref="IHost.Services"/>.
/// </summary>
/// <param name="configureDelegate">The delegate for configuring the <see cref="IConfigurationBuilder"/> that will be used
/// to construct the <see cref="IConfiguration"/> for the host.</param>
/// <returns>The same instance of the <see cref="IHostBuilder"/> for chaining.</returns>
public IHostBuilder ConfigureAppConfiguration(Action<HostBuilderContext, IConfigurationBuilder> configureDelegate)
{
_configureAppConfigActions.Add(configureDelegate ?? throw new ArgumentNullException(nameof(configureDelegate)));
return this;
}
/// <summary>
/// Adds services to the container. This can be called multiple times and the results will be additive.
/// </summary>
/// <param name="configureDelegate">The delegate for configuring the <see cref="IConfigurationBuilder"/> that will be used
/// to construct the <see cref="IConfiguration"/> for the host.</param>
/// <returns>The same instance of the <see cref="IHostBuilder"/> for chaining.</returns>
public IHostBuilder ConfigureServices(Action<HostBuilderContext, IServiceCollection> configureDelegate)
{
_configureServicesActions.Add(configureDelegate ?? throw new ArgumentNullException(nameof(configureDelegate)));
return this;
}
/// <summary>
/// Overrides the factory used to create the service provider.
/// </summary>
/// <typeparam name="TContainerBuilder">The type of the builder to create.</typeparam>
/// <param name="factory">A factory used for creating service providers.</param>
/// <returns>The same instance of the <see cref="IHostBuilder"/> for chaining.</returns>
public IHostBuilder UseServiceProviderFactory<TContainerBuilder>(IServiceProviderFactory<TContainerBuilder> factory)
{
_serviceProviderFactory = new ServiceFactoryAdapter<TContainerBuilder>(factory ?? throw new ArgumentNullException(nameof(factory)));
return this;
}
/// <summary>
/// Overrides the factory used to create the service provider.
/// </summary>
/// <param name="factory">A factory used for creating service providers.</param>
/// <typeparam name="TContainerBuilder">The type of the builder to create.</typeparam>
/// <returns>The same instance of the <see cref="IHostBuilder"/> for chaining.</returns>
public IHostBuilder UseServiceProviderFactory<TContainerBuilder>(Func<HostBuilderContext, IServiceProviderFactory<TContainerBuilder>> factory)
{
_serviceProviderFactory = new ServiceFactoryAdapter<TContainerBuilder>(() => _hostBuilderContext, factory ?? throw new ArgumentNullException(nameof(factory)));
return this;
}
/// <summary>
/// Enables configuring the instantiated dependency container. This can be called multiple times and
/// the results will be additive.
/// </summary>
/// <typeparam name="TContainerBuilder">The type of the builder to create.</typeparam>
/// <param name="configureDelegate">The delegate for configuring the <see cref="IConfigurationBuilder"/> that will be used
/// to construct the <see cref="IConfiguration"/> for the host.</param>
/// <returns>The same instance of the <see cref="IHostBuilder"/> for chaining.</returns>
public IHostBuilder ConfigureContainer<TContainerBuilder>(Action<HostBuilderContext, TContainerBuilder> configureDelegate)
{
_configureContainerActions.Add(new ConfigureContainerAdapter<TContainerBuilder>(configureDelegate
?? throw new ArgumentNullException(nameof(configureDelegate))));
return this;
}
/// <summary>
/// Run the given actions to initialize the host. This can only be called once.
/// </summary>
/// <returns>An initialized <see cref="IHost"/></returns>
public IHost Build()
{
if (_hostBuilt)
{
throw new InvalidOperationException("Build can only be called once.");
}
_hostBuilt = true;
BuildHostConfiguration();
CreateHostingEnvironment();
CreateHostBuilderContext();
BuildAppConfiguration();
CreateServiceProvider();
return _appServices.GetRequiredService<IHost>();
}
private void BuildHostConfiguration()
{
var configBuilder = new ConfigurationBuilder()
.AddInMemoryCollection(); // Make sure there's some default storage since there are no default providers
foreach (var buildAction in _configureHostConfigActions)
{
buildAction(configBuilder);
}
_hostConfiguration = configBuilder.Build();
}
private void CreateHostingEnvironment()
{
_hostingEnvironment = new HostingEnvironment()
{
ApplicationName = _hostConfiguration[HostDefaults.ApplicationKey],
EnvironmentName = _hostConfiguration[HostDefaults.EnvironmentKey] ?? Environments.Production,
ContentRootPath = ResolveContentRootPath(_hostConfiguration[HostDefaults.ContentRootKey], AppContext.BaseDirectory),
};
if (string.IsNullOrEmpty(_hostingEnvironment.ApplicationName))
{
// Note GetEntryAssembly returns null for the net4x console test runner.
_hostingEnvironment.ApplicationName = Assembly.GetEntryAssembly()?.GetName().Name;
}
_hostingEnvironment.ContentRootFileProvider = new PhysicalFileProvider(_hostingEnvironment.ContentRootPath);
}
private string ResolveContentRootPath(string contentRootPath, string basePath)
{
if (string.IsNullOrEmpty(contentRootPath))
{
return basePath;
}
if (Path.IsPathRooted(contentRootPath))
{
return contentRootPath;
}
return Path.Combine(Path.GetFullPath(basePath), contentRootPath);
}
private void CreateHostBuilderContext()
{
_hostBuilderContext = new HostBuilderContext(Properties)
{
HostingEnvironment = _hostingEnvironment,
Configuration = _hostConfiguration
};
}
private void BuildAppConfiguration()
{
var configBuilder = new ConfigurationBuilder()
.SetBasePath(_hostingEnvironment.ContentRootPath)
.AddConfiguration(_hostConfiguration, shouldDisposeConfiguration: true);
foreach (var buildAction in _configureAppConfigActions)
{
buildAction(_hostBuilderContext, configBuilder);
}
_appConfiguration = configBuilder.Build();
_hostBuilderContext.Configuration = _appConfiguration;
}
private void CreateServiceProvider()
{
var services = new ServiceCollection();
#pragma warning disable CS0618 // Type or member is obsolete
services.AddSingleton<IHostingEnvironment>(_hostingEnvironment);
#pragma warning restore CS0618 // Type or member is obsolete
services.AddSingleton<IHostEnvironment>(_hostingEnvironment);
services.AddSingleton(_hostBuilderContext);
// register configuration as factory to make it dispose with the service provider
services.AddSingleton(_ => _appConfiguration);
#pragma warning disable CS0618 // Type or member is obsolete
services.AddSingleton<IApplicationLifetime>(s => (IApplicationLifetime)s.GetService<IHostApplicationLifetime>());
#pragma warning restore CS0618 // Type or member is obsolete
services.AddSingleton<IHostApplicationLifetime, ApplicationLifetime>();
services.AddSingleton<IHostLifetime, ConsoleLifetime>();
services.AddSingleton<IHost, Internal.Host>();
services.AddOptions();
services.AddLogging();
foreach (var configureServicesAction in _configureServicesActions)
{
configureServicesAction(_hostBuilderContext, services);
}
var containerBuilder = _serviceProviderFactory.CreateBuilder(services);
foreach (var containerAction in _configureContainerActions)
{
containerAction.ConfigureContainer(_hostBuilderContext, containerBuilder);
}
_appServices = _serviceProviderFactory.CreateServiceProvider(containerBuilder);
if (_appServices == null)
{
throw new InvalidOperationException($"The IServiceProviderFactory returned a null IServiceProvider.");
}
// resolve configuration explicitly once to mark it as resolved within the
// service provider, ensuring it will be properly disposed with the provider
_ = _appServices.GetService<IConfiguration>();
}
}
}
仔细阅读后可以发现其实 ConfigureAppConfiguration(...) 这个方法就只是将 Action<HostBuilderContext, IConfigurationBuilder> 类型的委托参数添加到 _configureAppConfigActions 这个集合中。
接着在构建的时候（即调用 Build() 方法时）调用 BuildAppConfiguration() 方法，该方法首先会去创建一个 ConfigurationBuilder 类型的对象 configBuilder ，然后遍历 _configureAppConfigActions 集合，执行该集合中所有的委托（其中调用委托时传递的参数之一就是这个 configBuilder 对象），最后调用 configBuilder.Build() 方法，该方法返回一个 ConfigurationRoot 类型的对象。
最终在调用 CreateServiceProvider() 方法时再将这个 ConfigurationRoot 类型的对象依赖注入给 IConfiguration 。
我们继续找到这个 ConfigurationBuilder 类的源码，如下所示：
// Copyright (c) .NET Foundation. All rights reserved.
// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
using System;
using System.Collections.Generic;
namespace Microsoft.Extensions.Configuration
{
/// <summary>
/// Used to build key/value based configuration settings for use in an application.
/// </summary>
public class ConfigurationBuilder : IConfigurationBuilder
{
/// <summary>
/// Returns the sources used to obtain configuration values.
/// </summary>
public IList<IConfigurationSource> Sources { get; } = new List<IConfigurationSource>();
/// <summary>
/// Gets a key/value collection that can be used to share data between the <see cref="IConfigurationBuilder"/>
/// and the registered <see cref="IConfigurationProvider"/>s.
/// </summary>
public IDictionary<string, object> Properties { get; } = new Dictionary<string, object>();
/// <summary>
/// Adds a new configuration source.
/// </summary>
/// <param name="source">The configuration source to add.</param>
/// <returns>The same <see cref="IConfigurationBuilder"/>.</returns>
public IConfigurationBuilder Add(IConfigurationSource source)
{
if (source == null)
{
throw new ArgumentNullException(nameof(source));
}
Sources.Add(source);
return this;
}
/// <summary>
/// Builds an <see cref="IConfiguration"/> with keys and values from the set of providers registered in
/// <see cref="Sources"/>.
/// </summary>
/// <returns>An <see cref="IConfigurationRoot"/> with keys and values from the registered providers.</returns>
public IConfigurationRoot Build()
{
var providers = new List<IConfigurationProvider>();
foreach (var source in Sources)
{
var provider = source.Build(this);
providers.Add(provider);
}
return new ConfigurationRoot(providers);
}
}
}
从ConfigurationBuilder类中可以看出在调用该类 Build() 方法的时候它会去遍历 IList<IConfigurationSource> Sources 这个集合，那么这个集合里面存放的到底是什么数据，它又是什么时候加进去的呢？
其实我们在调用 hostBuilder.ConfigureAppConfiguration(...) 这个方法时传递的委托参数中的 config.AddJsonFile(...) 这个操作就是往 IList<IConfigurationSource> Sources 这个集合里面添加数据。
我们找到 Program.cs 类，将光标移动到 .AddJsonFile(...) 后按 F12 ，这样就可以定位找到 JsonConfigurationExtensions 类，如下所示：
接着我们去找到 Microsoft.Extensions.Configuration.JsonConfigurationExtensions 类的源码，如下所示：
// Copyright (c) .NET Foundation. All rights reserved.
// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
using System;
using System.IO;
using Microsoft.Extensions.Configuration.Json;
using Microsoft.Extensions.FileProviders;
namespace Microsoft.Extensions.Configuration
{
/// <summary>
/// Extension methods for adding <see cref="JsonConfigurationProvider"/>.
/// </summary>
public static class JsonConfigurationExtensions
{
/// <summary>
/// Adds the JSON configuration provider at <paramref name="path"/> to <paramref name="builder"/>.
/// </summary>
/// <param name="builder">The <see cref="IConfigurationBuilder"/> to add to.</param>
/// <param name="path">Path relative to the base path stored in
/// <see cref="IConfigurationBuilder.Properties"/> of <paramref name="builder"/>.</param>
/// <returns>The <see cref="IConfigurationBuilder"/>.</returns>
public static IConfigurationBuilder AddJsonFile(this IConfigurationBuilder builder, string path)
{
return AddJsonFile(builder, provider: null, path: path, optional: false, reloadOnChange: false);
}
/// <summary>
/// Adds the JSON configuration provider at <paramref name="path"/> to <paramref name="builder"/>.
/// </summary>
/// <param name="builder">The <see cref="IConfigurationBuilder"/> to add to.</param>
/// <param name="path">Path relative to the base path stored in
/// <see cref="IConfigurationBuilder.Properties"/> of <paramref name="builder"/>.</param>
/// <param name="optional">Whether the file is optional.</param>
/// <returns>The <see cref="IConfigurationBuilder"/>.</returns>
public static IConfigurationBuilder AddJsonFile(this IConfigurationBuilder builder, string path, bool optional)
{
return AddJsonFile(builder, provider: null, path: path, optional: optional, reloadOnChange: false);
}
/// <summary>
/// Adds the JSON configuration provider at <paramref name="path"/> to <paramref name="builder"/>.
/// </summary>
/// <param name="builder">The <see cref="IConfigurationBuilder"/> to add to.</param>
/// <param name="path">Path relative to the base path stored in
/// <see cref="IConfigurationBuilder.Properties"/> of <paramref name="builder"/>.</param>
/// <param name="optional">Whether the file is optional.</param>
/// <param name="reloadOnChange">Whether the configuration should be reloaded if the file changes.</param>
/// <returns>The <see cref="IConfigurationBuilder"/>.</returns>
public static IConfigurationBuilder AddJsonFile(this IConfigurationBuilder builder, string path, bool optional, bool reloadOnChange)
{
return AddJsonFile(builder, provider: null, path: path, optional: optional, reloadOnChange: reloadOnChange);
}
/// <summary>
/// Adds a JSON configuration source to <paramref name="builder"/>.
/// </summary>
/// <param name="builder">The <see cref="IConfigurationBuilder"/> to add to.</param>
/// <param name="provider">The <see cref="IFileProvider"/> to use to access the file.</param>
/// <param name="path">Path relative to the base path stored in
/// <see cref="IConfigurationBuilder.Properties"/> of <paramref name="builder"/>.</param>
/// <param name="optional">Whether the file is optional.</param>
/// <param name="reloadOnChange">Whether the configuration should be reloaded if the file changes.</param>
/// <returns>The <see cref="IConfigurationBuilder"/>.</returns>
public static IConfigurationBuilder AddJsonFile(this IConfigurationBuilder builder, IFileProvider provider, string path, bool optional, bool reloadOnChange)
{
if (builder == null)
{
throw new ArgumentNullException(nameof(builder));
}
if (string.IsNullOrEmpty(path))
{
throw new ArgumentException(Resources.Error_InvalidFilePath, nameof(path));
}
return builder.AddJsonFile(s =>
{
s.FileProvider = provider;
s.Path = path;
s.Optional = optional;
s.ReloadOnChange = reloadOnChange;
s.ResolveFileProvider();
});
}
/// <summary>
/// Adds a JSON configuration source to <paramref name="builder"/>.
/// </summary>
/// <param name="builder">The <see cref="IConfigurationBuilder"/> to add to.</param>
/// <param name="configureSource">Configures the source.</param>
/// <returns>The <see cref="IConfigurationBuilder"/>.</returns>
public static IConfigurationBuilder AddJsonFile(this IConfigurationBuilder builder, Action<JsonConfigurationSource> configureSource)
=> builder.Add(configureSource);
/// <summary>
/// Adds a JSON configuration source to <paramref name="builder"/>.
/// </summary>
/// <param name="builder">The <see cref="IConfigurationBuilder"/> to add to.</param>
/// <param name="stream">The <see cref="Stream"/> to read the json configuration data from.</param>
/// <returns>The <see cref="IConfigurationBuilder"/>.</returns>
public static IConfigurationBuilder AddJsonStream(this IConfigurationBuilder builder, Stream stream)
{
if (builder == null)
{
throw new ArgumentNullException(nameof(builder));
}
return builder.Add<JsonStreamConfigurationSource>(s => s.Stream = stream);
}
}
}
Microsoft.Extensions.Configuration.JsonConfigurationExtensions类源码
然后定位找到对应的 AddJsonFile 方法，如下所示：
/// <summary>
/// Adds the JSON configuration provider at <paramref name="path"/> to <paramref name="builder"/>.
/// </summary>
/// <param name="builder">The <see cref="IConfigurationBuilder"/> to add to.</param>
/// <param name="path">Path relative to the base path stored in
/// <see cref="IConfigurationBuilder.Properties"/> of <paramref name="builder"/>.</param>
/// <param name="optional">Whether the file is optional.</param>
/// <param name="reloadOnChange">Whether the configuration should be reloaded if the file changes.</param>
/// <returns>The <see cref="IConfigurationBuilder"/>.</returns>
public static IConfigurationBuilder AddJsonFile(this IConfigurationBuilder builder, string path, bool optional, bool reloadOnChange)
{
return AddJsonFile(builder, provider: null, path: path, optional: optional, reloadOnChange: reloadOnChange);
}
接着按 F12 会找到如下方法：
/// <summary>
/// Adds a JSON configuration source to <paramref name="builder"/>.
/// </summary>
/// <param name="builder">The <see cref="IConfigurationBuilder"/> to add to.</param>
/// <param name="provider">The <see cref="IFileProvider"/> to use to access the file.</param>
/// <param name="path">Path relative to the base path stored in
/// <see cref="IConfigurationBuilder.Properties"/> of <paramref name="builder"/>.</param>
/// <param name="optional">Whether the file is optional.</param>
/// <param name="reloadOnChange">Whether the configuration should be reloaded if the file changes.</param>
/// <returns>The <see cref="IConfigurationBuilder"/>.</returns>
public static IConfigurationBuilder AddJsonFile(this IConfigurationBuilder builder, IFileProvider provider, string path, bool optional, bool reloadOnChange)
{
if (builder == null)
{
throw new ArgumentNullException(nameof(builder));
}
if (string.IsNullOrEmpty(path))
{
throw new ArgumentException(Resources.Error_InvalidFilePath, nameof(path));
}
return builder.AddJsonFile(s =>
{
s.FileProvider = provider;
s.Path = path;
s.Optional = optional;
s.ReloadOnChange = reloadOnChange;
s.ResolveFileProvider();
});
}
继续按 F12 找到如下方法：
/// <summary>
/// Adds a JSON configuration source to <paramref name="builder"/>.
/// </summary>
/// <param name="builder">The <see cref="IConfigurationBuilder"/> to add to.</param>
/// <param name="configureSource">Configures the source.</param>
/// <returns>The <see cref="IConfigurationBuilder"/>.</returns>
public static IConfigurationBuilder AddJsonFile(this IConfigurationBuilder builder, Action<JsonConfigurationSource> configureSource)
=> builder.Add(configureSource);
可以发现它最终是调用 builder.Add(...) 这个扩展方法的，该扩展方法位于 Microsoft.Extensions.Configuration.ConfigurationExtensions 类中。
我们找到 ConfigurationExtensions 类的源码，如下所示：
// Copyright (c) .NET Foundation. All rights reserved.
// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
using System;
using System.Collections.Generic;
using System.Linq;
namespace Microsoft.Extensions.Configuration
{
/// <summary>
/// Extension methods for configuration classes./>.
/// </summary>
public static class ConfigurationExtensions
{
/// <summary>
/// Adds a new configuration source.
/// </summary>
/// <param name="builder">The <see cref="IConfigurationBuilder"/> to add to.</param>
/// <param name="configureSource">Configures the source secrets.</param>
/// <returns>The <see cref="IConfigurationBuilder"/>.</returns>
public static IConfigurationBuilder Add<TSource>(this IConfigurationBuilder builder, Action<TSource> configureSource) where TSource : IConfigurationSource, new()
{
var source = new TSource();
configureSource?.Invoke(source);
return builder.Add(source);
}
/// <summary>
/// Shorthand for GetSection("ConnectionStrings")[name].
/// </summary>
/// <param name="configuration">The configuration.</param>
/// <param name="name">The connection string key.</param>
/// <returns>The connection string.</returns>
public static string GetConnectionString(this IConfiguration configuration, string name)
{
return configuration?.GetSection("ConnectionStrings")?[name];
}
/// <summary>
/// Get the enumeration of key value pairs within the <see cref="IConfiguration" />
/// </summary>
/// <param name="configuration">The <see cref="IConfiguration"/> to enumerate.</param>
/// <returns>An enumeration of key value pairs.</returns>
public static IEnumerable<KeyValuePair<string, string>> AsEnumerable(this IConfiguration configuration) => configuration.AsEnumerable(makePathsRelative: false);
/// <summary>
/// Get the enumeration of key value pairs within the <see cref="IConfiguration" />
/// </summary>
/// <param name="configuration">The <see cref="IConfiguration"/> to enumerate.</param>
/// <param name="makePathsRelative">If true, the child keys returned will have the current configuration's Path trimmed from the front.</param>
/// <returns>An enumeration of key value pairs.</returns>
public static IEnumerable<KeyValuePair<string, string>> AsEnumerable(this IConfiguration configuration, bool makePathsRelative)
{
var stack = new Stack<IConfiguration>();
stack.Push(configuration);
var rootSection = configuration as IConfigurationSection;
var prefixLength = (makePathsRelative && rootSection != null) ? rootSection.Path.Length + 1 : 0;
while (stack.Count > 0)
{
var config = stack.Pop();
// Don't include the sections value if we are removing paths, since it will be an empty key
if (config is IConfigurationSection section && (!makePathsRelative || config != configuration))
{
yield return new KeyValuePair<string, string>(section.Path.Substring(prefixLength), section.Value);
}
foreach (var child in config.GetChildren())
{
stack.Push(child);
}
}
}
/// <summary>
/// Determines whether the section has a <see cref="IConfigurationSection.Value"/> or has children
/// </summary>
public static bool Exists(this IConfigurationSection section)
{
if (section == null)
{
return false;
}
return section.Value != null || section.GetChildren().Any();
}
}
}
Microsoft.Extensions.Configuration.ConfigurationExtensions类源码
从中找到对应的扩展方法：
/// <summary>
/// Adds a new configuration source.
/// </summary>
/// <param name="builder">The <see cref="IConfigurationBuilder"/> to add to.</param>
/// <param name="configureSource">Configures the source secrets.</param>
/// <returns>The <see cref="IConfigurationBuilder"/>.</returns>
public static IConfigurationBuilder Add<TSource>(this IConfigurationBuilder builder, Action<TSource> configureSource) where TSource : IConfigurationSource, new()
{
var source = new TSource();
configureSource?.Invoke(source);
return builder.Add(source);
}
由此可见 config.AddJsonFile(...) 这个方法最终会变成调用 ConfigurationBuilder 类中的 Add(...) 方法，传递 JsonConfigurationSource 类型的对象。
下面我们继续往下分析 ConfigurationBuilder 类的源码：
// Copyright (c) .NET Foundation. All rights reserved.
// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
using System;
using System.Collections.Generic;
namespace Microsoft.Extensions.Configuration
{
/// <summary>
/// Used to build key/value based configuration settings for use in an application.
/// </summary>
public class ConfigurationBuilder : IConfigurationBuilder
{
/// <summary>
/// Returns the sources used to obtain configuration values.
/// </summary>
public IList<IConfigurationSource> Sources { get; } = new List<IConfigurationSource>();
/// <summary>
/// Gets a key/value collection that can be used to share data between the <see cref="IConfigurationBuilder"/>
/// and the registered <see cref="IConfigurationProvider"/>s.
/// </summary>
public IDictionary<string, object> Properties { get; } = new Dictionary<string, object>();
/// <summary>
/// Adds a new configuration source.
/// </summary>
/// <param name="source">The configuration source to add.</param>
/// <returns>The same <see cref="IConfigurationBuilder"/>.</returns>
public IConfigurationBuilder Add(IConfigurationSource source)
{
if (source == null)
{
throw new ArgumentNullException(nameof(source));
}
Sources.Add(source);
return this;
}
/// <summary>
/// Builds an <see cref="IConfiguration"/> with keys and values from the set of providers registered in
/// <see cref="Sources"/>.
/// </summary>
/// <returns>An <see cref="IConfigurationRoot"/> with keys and values from the registered providers.</returns>
public IConfigurationRoot Build()
{
var providers = new List<IConfigurationProvider>();
foreach (var source in Sources)
{
var provider = source.Build(this);
providers.Add(provider);
}
return new ConfigurationRoot(providers);
}
}
}
从上文的分析中我们已经知道此时 IList<IConfigurationSource> Sources 这个集合中存放的其实就是 JsonConfigurationSource 类型的对象。
我们找到 JsonConfigurationSource 类的源码：
// Copyright (c) .NET Foundation. All rights reserved.
// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
using System;
namespace Microsoft.Extensions.Configuration.Json
{
/// <summary>
/// Represents a JSON file as an <see cref="IConfigurationSource"/>.
/// </summary>
public class JsonConfigurationSource : FileConfigurationSource
{
/// <summary>
/// Builds the <see cref="JsonConfigurationProvider"/> for this source.
/// </summary>
/// <param name="builder">The <see cref="IConfigurationBuilder"/>.</param>
/// <returns>A <see cref="JsonConfigurationProvider"/></returns>
public override IConfigurationProvider Build(IConfigurationBuilder builder)
{
EnsureDefaults(builder);
return new JsonConfigurationProvider(this);
}
}
}
从中我们可以知道 JsonConfigurationSource 中的 Build(...) 方法返回的是 JsonConfigurationProvider 类型的对象。
至此，我们就清楚了 ConfigurationBuilder 类中的 Build(...) 方法返回的是 new ConfigurationRoot(providers) ，而 providers 集合里面存放的就是 JsonConfigurationProvider 类型的对象。
我们继续找到 ConfigurationRoot 类的源码，如下所示：
// Copyright (c) .NET Foundation. All rights reserved.
// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading;
using Microsoft.Extensions.Primitives;
namespace Microsoft.Extensions.Configuration
{
/// <summary>
/// The root node for a configuration.
/// </summary>
public class ConfigurationRoot : IConfigurationRoot, IDisposable
{
private readonly IList<IConfigurationProvider> _providers;
private readonly IList<IDisposable> _changeTokenRegistrations;
private ConfigurationReloadToken _changeToken = new ConfigurationReloadToken();
/// <summary>
/// Initializes a Configuration root with a list of providers.
/// </summary>
/// <param name="providers">The <see cref="IConfigurationProvider"/>s for this configuration.</param>
public ConfigurationRoot(IList<IConfigurationProvider> providers)
{
if (providers == null)
{
throw new ArgumentNullException(nameof(providers));
}
_providers = providers;
_changeTokenRegistrations = new List<IDisposable>(providers.Count);
foreach (var p in providers)
{
p.Load();
_changeTokenRegistrations.Add(ChangeToken.OnChange(() => p.GetReloadToken(), () => RaiseChanged()));
}
}
/// <summary>
/// The <see cref="IConfigurationProvider"/>s for this configuration.
/// </summary>
public IEnumerable<IConfigurationProvider> Providers => _providers;
/// <summary>
/// Gets or sets the value corresponding to a configuration key.
/// </summary>
/// <param name="key">The configuration key.</param>
/// <returns>The configuration value.</returns>
public string this[string key]
{
get
{
for (var i = _providers.Count - 1; i >= 0; i--)
{
var provider = _providers[i];
if (provider.TryGet(key, out var value))
{
return value;
}
}
return null;
}
set
{
if (!_providers.Any())
{
throw new InvalidOperationException(Resources.Error_NoSources);
}
foreach (var provider in _providers)
{
provider.Set(key, value);
}
}
}
/// <summary>
/// Gets the immediate children sub-sections.
/// </summary>
/// <returns>The children.</returns>
public IEnumerable<IConfigurationSection> GetChildren() => this.GetChildrenImplementation(null);
/// <summary>
/// Returns a <see cref="IChangeToken"/> that can be used to observe when this configuration is reloaded.
/// </summary>
/// <returns>The <see cref="IChangeToken"/>.</returns>
public IChangeToken GetReloadToken() => _changeToken;
/// <summary>
/// Gets a configuration sub-section with the specified key.
/// </summary>
/// <param name="key">The key of the configuration section.</param>
/// <returns>The <see cref="IConfigurationSection"/>.</returns>
/// <remarks>
/// This method will never return <c>null</c>. If no matching sub-section is found with the specified key,
/// an empty <see cref="IConfigurationSection"/> will be returned.
/// </remarks>
public IConfigurationSection GetSection(string key)
=> new ConfigurationSection(this, key);
/// <summary>
/// Force the configuration values to be reloaded from the underlying sources.
/// </summary>
public void Reload()
{
foreach (var provider in _providers)
{
provider.Load();
}
RaiseChanged();
}
private void RaiseChanged()
{
var previousToken = Interlocked.Exchange(ref _changeToken, new ConfigurationReloadToken());
previousToken.OnReload();
}
/// <inheritdoc />
public void Dispose()
{
// dispose change token registrations
foreach (var registration in _changeTokenRegistrations)
{
registration.Dispose();
}
// dispose providers
foreach (var provider in _providers)
{
(provider as IDisposable)?.Dispose();
}
}
}
}
其中 ConfigurationSection 类的源码如下：
// Copyright (c) .NET Foundation. All rights reserved.
// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
using System;
using System.Collections.Generic;
using Microsoft.Extensions.Primitives;
namespace Microsoft.Extensions.Configuration
{
/// <summary>
/// Represents a section of application configuration values.
/// </summary>
public class ConfigurationSection : IConfigurationSection
{
private readonly IConfigurationRoot _root;
private readonly string _path;
private string _key;
/// <summary>
/// Initializes a new instance.
/// </summary>
/// <param name="root">The configuration root.</param>
/// <param name="path">The path to this section.</param>
public ConfigurationSection(IConfigurationRoot root, string path)
{
if (root == null)
{
throw new ArgumentNullException(nameof(root));
}
if (path == null)
{
throw new ArgumentNullException(nameof(path));
}
_root = root;
_path = path;
}
/// <summary>
/// Gets the full path to this section from the <see cref="IConfigurationRoot"/>.
/// </summary>
public string Path => _path;
/// <summary>
/// Gets the key this section occupies in its parent.
/// </summary>
public string Key
{
get
{
if (_key == null)
{
// Key is calculated lazily as last portion of Path
_key = ConfigurationPath.GetSectionKey(_path);
}
return _key;
}
}
/// <summary>
/// Gets or sets the section value.
/// </summary>
public string Value
{
get
{
return _root[Path];
}
set
{
_root[Path] = value;
}
}
/// <summary>
/// Gets or sets the value corresponding to a configuration key.
/// </summary>
/// <param name="key">The configuration key.</param>
/// <returns>The configuration value.</returns>
public string this[string key]
{
get
{
return _root[ConfigurationPath.Combine(Path, key)];
}
set
{
_root[ConfigurationPath.Combine(Path, key)] = value;
}
}
/// <summary>
/// Gets a configuration sub-section with the specified key.
/// </summary>
/// <param name="key">The key of the configuration section.</param>
/// <returns>The <see cref="IConfigurationSection"/>.</returns>
/// <remarks>
/// This method will never return <c>null</c>. If no matching sub-section is found with the specified key,
/// an empty <see cref="IConfigurationSection"/> will be returned.
/// </remarks>
public IConfigurationSection GetSection(string key) => _root.GetSection(ConfigurationPath.Combine(Path, key));
/// <summary>
/// Gets the immediate descendant configuration sub-sections.
/// </summary>
/// <returns>The configuration sub-sections.</returns>
public IEnumerable<IConfigurationSection> GetChildren() => _root.GetChildrenImplementation(Path);
/// <summary>
/// Returns a <see cref="IChangeToken"/> that can be used to observe when this configuration is reloaded.
/// </summary>
/// <returns>The <see cref="IChangeToken"/>.</returns>
public IChangeToken GetReloadToken() => _root.GetReloadToken();
}
}
Microsoft.Extensions.Configuration.ConfigurationSection类源码
仔细观察上面的源码后我们可以发现：
1、在ConfigurationRoot类的构造函数中它会依次调用传递过来的Provider的Load方法去加载数据。
2、使用ConfigurationRoot索引器取数据的时候，它会逆序依次调用Provider的TryGet方法获取数据，如果成功就直接返回，这就是为什么后添加的数据源会覆盖之前添加的数据源。
3、在创建ConfigurationSection的时候会把ConfigurationRoot传递进去，而ConfigurationSection取数据的时候也是通过ConfigurationRoot来取的，实际上ConfigurationSection并不包含任何实际的配置数据。
接下来我们就来看一下它是如何加载数据的，找到 JsonConfigurationProvider 类的源码，如下所示：
// Copyright (c) .NET Foundation. All rights reserved.
// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
using System;
using System.Collections.Generic;
using System.IO;
using System.Text.Json;
namespace Microsoft.Extensions.Configuration.Json
{
/// <summary>
/// A JSON file based <see cref="FileConfigurationProvider"/>.
/// </summary>
public class JsonConfigurationProvider : FileConfigurationProvider
{
/// <summary>
/// Initializes a new instance with the specified source.
/// </summary>
/// <param name="source">The source settings.</param>
public JsonConfigurationProvider(JsonConfigurationSource source) : base(source) { }
/// <summary>
/// Loads the JSON data from a stream.
/// </summary>
/// <param name="stream">The stream to read.</param>
public override void Load(Stream stream)
{
try
{
Data = JsonConfigurationFileParser.Parse(stream);
}
catch (JsonException e)
{
throw new FormatException(Resources.Error_JSONParseError, e);
}
}
}
}
它是继承 FileConfigurationProvider 类，我们找到 FileConfigurationProvider 类的源码：
// Copyright (c) .NET Foundation. All rights reserved.
// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
using System;
using System.Collections.Generic;
using System.IO;
using System.Runtime.ExceptionServices;
using System.Text;
using System.Threading;
using Microsoft.Extensions.Primitives;
namespace Microsoft.Extensions.Configuration
{
/// <summary>
/// Base class for file based <see cref="ConfigurationProvider"/>.
/// </summary>
public abstract class FileConfigurationProvider : ConfigurationProvider, IDisposable
{
private readonly IDisposable _changeTokenRegistration;
/// <summary>
/// Initializes a new instance with the specified source.
/// </summary>
/// <param name="source">The source settings.</param>
public FileConfigurationProvider(FileConfigurationSource source)
{
if (source == null)
{
throw new ArgumentNullException(nameof(source));
}
Source = source;
if (Source.ReloadOnChange && Source.FileProvider != null)
{
_changeTokenRegistration = ChangeToken.OnChange(
() => Source.FileProvider.Watch(Source.Path),
() => {
Thread.Sleep(Source.ReloadDelay);
Load(reload: true);
});
}
}
/// <summary>
/// The source settings for this provider.
/// </summary>
public FileConfigurationSource Source { get; }
/// <summary>
/// Generates a string representing this provider name and relevant details.
/// </summary>
/// <returns> The configuration name. </returns>
public override string ToString()
=> $"{GetType().Name} for '{Source.Path}' ({(Source.Optional ? "Optional" : "Required")})";
private void Load(bool reload)
{
var file = Source.FileProvider?.GetFileInfo(Source.Path);
if (file == null || !file.Exists)
{
if (Source.Optional || reload) // Always optional on reload
{
Data = new Dictionary<string, string>(StringComparer.OrdinalIgnoreCase);
}
else
{
var error = new StringBuilder($"The configuration file '{Source.Path}' was not found and is not optional.");
if (!string.IsNullOrEmpty(file?.PhysicalPath))
{
error.Append($" The physical path is '{file.PhysicalPath}'.");
}
HandleException(ExceptionDispatchInfo.Capture(new FileNotFoundException(error.ToString())));
}
}
else
{
// Always create new Data on reload to drop old keys
if (reload)
{
Data = new Dictionary<string, string>(StringComparer.OrdinalIgnoreCase);
}
using (var stream = file.CreateReadStream())
{
try
{
Load(stream);
}
catch (Exception e)
{
HandleException(ExceptionDispatchInfo.Capture(e));
}
}
}
// REVIEW: Should we raise this in the base as well / instead?
OnReload();
}
/// <summary>
/// Loads the contents of the file at <see cref="Path"/>.
/// </summary>
/// <exception cref="FileNotFoundException">If Optional is <c>false</c> on the source and a
/// file does not exist at specified Path.</exception>
public override void Load()
{
Load(reload: false);
}
/// <summary>
/// Loads this provider's data from a stream.
/// </summary>
/// <param name="stream">The stream to read.</param>
public abstract void Load(Stream stream);
private void HandleException(ExceptionDispatchInfo info)
{
bool ignoreException = false;
if (Source.OnLoadException != null)
{
var exceptionContext = new FileLoadExceptionContext
{
Provider = this,
Exception = info.SourceException
};
Source.OnLoadException.Invoke(exceptionContext);
ignoreException = exceptionContext.Ignore;
}
if (!ignoreException)
{
info.Throw();
}
}
/// <inheritdoc />
public void Dispose() => Dispose(true);
/// <summary>
/// Dispose the provider.
/// </summary>
/// <param name="disposing"><c>true</c> if invoked from <see cref="IDisposable.Dispose"/>.</param>
protected virtual void Dispose(bool disposing)
{
_changeTokenRegistration?.Dispose();
}
}
}
Microsoft.Extensions.Configuration.FileConfigurationProvider类源码
仔细阅读 JsonConfigurationProvider 和 FileConfigurationProvider 这两个类的源码后，可以知道它最终是通过 JsonConfigurationFileParser.Parse(stream) 这个操作来加载数据的。
并且 FileConfigurationProvider 类继承自 ConfigurationProvider 类，我们找到 ConfigurationProvider 和 JsonConfigurationFileParser 这两个类的源码，如下所示：
ConfigurationProvider类源码如下：
// Copyright (c) .NET Foundation. All rights reserved.
// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading;
using Microsoft.Extensions.Primitives;
namespace Microsoft.Extensions.Configuration
{
/// <summary>
/// Base helper class for implementing an <see cref="IConfigurationProvider"/>
/// </summary>
public abstract class ConfigurationProvider : IConfigurationProvider
{
private ConfigurationReloadToken _reloadToken = new ConfigurationReloadToken();
/// <summary>
/// Initializes a new <see cref="IConfigurationProvider"/>
/// </summary>
protected ConfigurationProvider()
{
Data = new Dictionary<string, string>(StringComparer.OrdinalIgnoreCase);
}
/// <summary>
/// The configuration key value pairs for this provider.
/// </summary>
protected IDictionary<string, string> Data { get; set; }
/// <summary>
/// Attempts to find a value with the given key, returns true if one is found, false otherwise.
/// </summary>
/// <param name="key">The key to lookup.</param>
/// <param name="value">The value found at key if one is found.</param>
/// <returns>True if key has a value, false otherwise.</returns>
public virtual bool TryGet(string key, out string value)
=> Data.TryGetValue(key, out value);
/// <summary>
/// Sets a value for a given key.
/// </summary>
/// <param name="key">The configuration key to set.</param>
/// <param name="value">The value to set.</param>
public virtual void Set(string key, string value)
=> Data[key] = value;
/// <summary>
/// Loads (or reloads) the data for this provider.
/// </summary>
public virtual void Load()
{ }
/// <summary>
/// Returns the list of keys that this provider has.
/// </summary>
/// <param name="earlierKeys">The earlier keys that other providers contain.</param>
/// <param name="parentPath">The path for the parent IConfiguration.</param>
/// <returns>The list of keys for this provider.</returns>
public virtual IEnumerable<string> GetChildKeys(
IEnumerable<string> earlierKeys,
string parentPath)
{
var prefix = parentPath == null ? string.Empty : parentPath + ConfigurationPath.KeyDelimiter;
return Data
.Where(kv => kv.Key.StartsWith(prefix, StringComparison.OrdinalIgnoreCase))
.Select(kv => Segment(kv.Key, prefix.Length))
.Concat(earlierKeys)
.OrderBy(k => k, ConfigurationKeyComparer.Instance);
}
private static string Segment(string key, int prefixLength)
{
var indexOf = key.IndexOf(ConfigurationPath.KeyDelimiter, prefixLength, StringComparison.OrdinalIgnoreCase);
return indexOf < 0 ? key.Substring(prefixLength) : key.Substring(prefixLength, indexOf - prefixLength);
}
/// <summary>
/// Returns a <see cref="IChangeToken"/> that can be used to listen when this provider is reloaded.
/// </summary>
/// <returns>The <see cref="IChangeToken"/>.</returns>
public IChangeToken GetReloadToken()
{
return _reloadToken;
}
/// <summary>
/// Triggers the reload change token and creates a new one.
/// </summary>
protected void OnReload()
{
var previousToken = Interlocked.Exchange(ref _reloadToken, new ConfigurationReloadToken());
previousToken.OnReload();
}
/// <summary>
/// Generates a string representing this provider name and relevant details.
/// </summary>
/// <returns> The configuration name. </returns>
public override string ToString() => $"{GetType().Name}";
}
}
JsonConfigurationFileParser类源码如下：
// Copyright (c) .NET Foundation. All rights reserved.
// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text.Json;
namespace Microsoft.Extensions.Configuration.Json
{
internal class JsonConfigurationFileParser
{
private JsonConfigurationFileParser() { }
private readonly IDictionary<string, string> _data = new SortedDictionary<string, string>(StringComparer.OrdinalIgnoreCase);
private readonly Stack<string> _context = new Stack<string>();
private string _currentPath;
public static IDictionary<string, string> Parse(Stream input)
=> new JsonConfigurationFileParser().ParseStream(input);
private IDictionary<string, string> ParseStream(Stream input)
{
_data.Clear();
var jsonDocumentOptions = new JsonDocumentOptions
{
CommentHandling = JsonCommentHandling.Skip,
AllowTrailingCommas = true,
};
using (var reader = new StreamReader(input))
using (JsonDocument doc = JsonDocument.Parse(reader.ReadToEnd(), jsonDocumentOptions))
{
if (doc.RootElement.ValueKind != JsonValueKind.Object)
{
throw new FormatException(Resources.FormatError_UnsupportedJSONToken(doc.RootElement.ValueKind));
}
VisitElement(doc.RootElement);
}
return _data;
}
private void VisitElement(JsonElement element) {
foreach (var property in element.EnumerateObject())
{
EnterContext(property.Name);
VisitValue(property.Value);
ExitContext();
}
}
private void VisitValue(JsonElement value)
{
switch (value.ValueKind) {
case JsonValueKind.Object:
VisitElement(value);
break;
case JsonValueKind.Array:
var index = 0;
foreach (var arrayElement in value.EnumerateArray()) {
EnterContext(index.ToString());
VisitValue(arrayElement);
ExitContext();
index++;
}
break;
case JsonValueKind.Number:
case JsonValueKind.String:
case JsonValueKind.True:
case JsonValueKind.False:
case JsonValueKind.Null:
var key = _currentPath;
if (_data.ContainsKey(key))
{
throw new FormatException(Resources.FormatError_KeyIsDuplicated(key));
}
_data[key] = value.ToString();
break;
default:
throw new FormatException(Resources.FormatError_UnsupportedJSONToken(value.ValueKind));
}
}
private void EnterContext(string context)
{
_context.Push(context);
_currentPath = ConfigurationPath.Combine(_context.Reverse());
}
private void ExitContext()
{
_context.Pop();
_currentPath = ConfigurationPath.Combine(_context.Reverse());
}
}
}
其中ConfigurationPath类源码如下：
// Copyright (c) .NET Foundation. All rights reserved.
// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
using System;
using System.Collections.Generic;
namespace Microsoft.Extensions.Configuration
{
/// <summary>
/// Utility methods and constants for manipulating Configuration paths
/// </summary>
public static class ConfigurationPath
{
/// <summary>
/// The delimiter ":" used to separate individual keys in a path.
/// </summary>
public static readonly string KeyDelimiter = ":";
/// <summary>
/// Combines path segments into one path.
/// </summary>
/// <param name="pathSegments">The path segments to combine.</param>
/// <returns>The combined path.</returns>
public static string Combine(params string[] pathSegments)
{
if (pathSegments == null)
{
throw new ArgumentNullException(nameof(pathSegments));
}
return string.Join(KeyDelimiter, pathSegments);
}
/// <summary>
/// Combines path segments into one path.
/// </summary>
/// <param name="pathSegments">The path segments to combine.</param>
/// <returns>The combined path.</returns>
public static string Combine(IEnumerable<string> pathSegments)
{
if (pathSegments == null)
{
throw new ArgumentNullException(nameof(pathSegments));
}
return string.Join(KeyDelimiter, pathSegments);
}
/// <summary>
/// Extracts the last path segment from the path.
/// </summary>
/// <param name="path">The path.</param>
/// <returns>The last path segment of the path.</returns>
public static string GetSectionKey(string path)
{
if (string.IsNullOrEmpty(path))
{
return path;
}
var lastDelimiterIndex = path.LastIndexOf(KeyDelimiter, StringComparison.OrdinalIgnoreCase);
return lastDelimiterIndex == -1 ? path : path.Substring(lastDelimiterIndex + 1);
}
/// <summary>
/// Extracts the path corresponding to the parent node for a given path.
/// </summary>
/// <param name="path">The path.</param>
/// <returns>The original path minus the last individual segment found in it. Null if the original path corresponds to a top level node.</returns>
public static string GetParentPath(string path)
{
if (string.IsNullOrEmpty(path))
{
return null;
}
var lastDelimiterIndex = path.LastIndexOf(KeyDelimiter, StringComparison.OrdinalIgnoreCase);
return lastDelimiterIndex == -1 ? null : path.Substring(0, lastDelimiterIndex);
}
}
}
Microsoft.Extensions.Configuration.ConfigurationPath类源码
仔细阅读与ConfigurationProvider类相关的源码后可以发现， 其实ConfigurationProvider只是一个抽象类，具体的需要由对应类型的Provider去实现，其实也只是需要实现Load方法，去填充那个字符串字典。而在实现的过程中需要用到ConfigurationPath这个静态类来帮助生成字典里的key，具体来说就是各层级之间用冒号 “:” 隔开，例如：“A:B:C” 。这个冒号是以静态只读的形式定义在ConfigurationPath类中的。
3、小结
四大配置对象的UML图如下所示：
1、IConfigurationBuilder：整个配置系统的核心，包含多个IConfigurationSource，利用它们产生多个IConfigurationProvider，最终是为了得到一个IConfigurationRoot对象，并将它注入到容器中。
2、IConfigurationProvider：实际包含配置信息的类，内部包含一个字符串字典，它由IConfigurationSource产生。
3、IConfigurationSource：包含了一个配置源的信息，以文件为例，包含了文件名和文件路径等，并不包含实际的配置信息。如果是基于数据库的数据源，它会包含数据库连接信息，SQL等。它的目的是为了产生一个IConfigurationProvider。
4、IConfigurationRoot：在获取配置信息时，直接操作的对象，内部包含一个IConfigurationProvider列表。
大致过程：首先是调用各类数据源类库提供的扩展方法往IConfigurationBuilder中添加数据源IConfigurationSource，之后IConfigurationBuilder会依次调用IConfigurationSource的Build方法产生对应的IConfigurationProvider，并将他们传入到IConfigurationRoot中，最终我们会拿到IConfigurationRoot进行使用。
本文部分内容参考博文：https://www.cnblogs.com/zhurongbo/p/10831284.html
至此本文就全部介绍完了，如果觉得对您有所启发请记得点个赞哦！！！
aspnetcore源码：
链接：https://pan.baidu.com/s/1fszyRzDw9di1hVvPIF4VYg 提取码：wz1j
Demo源码：
链接：https://pan.baidu.com/s/1AdV-cwWnIKNx81WQqEXUdg 提取码：ki9c
此文由博主精心撰写转载请保留此原文链接：https://www.cnblogs.com/xyh9039/p/15916859.html
版权声明：如有雷同纯属巧合，如有侵权请及时联系本人修改，谢谢！！！
出处：https://www.cnblogs.com/xyh9039/p/15916859.html
标签：Core,ASP,string,源码,new,using,path,configuration,public From： https://www.cnblogs.com/mq0036/p/17565957.html