asp.net core 默认配置

Configuration

asp.net core  默认的 appsettings.json 配置是如果注入到承载主机的，

创建 一个asp.net core  MVC 或者api程序，Program.cs 都可以看见承载主机如下：

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IHostBuilder CreateHostBuilder(string[] args) =>       Host.CreateDefaultBuilder(args) ... Build()

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1	CreateDefaultBuilder的实现：

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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.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, loggingBuilder) => { loggingBuilder.Configure(options => { options.ActivityTrackingOptions = ActivityTrackingOptions.SpanId | ActivityTrackingOptions.TraceId | ActivityTrackingOptions.ParentId; }); loggingBuilder.AddConfiguration(hostingContext.Configuration.GetSection("Logging")); loggingBuilder.AddConsole(); loggingBuilder.AddDebug(); loggingBuilder.AddEventSourceLogger(); }). UseDefaultServiceProvider((context, options) => { options.ValidateScopes = context.HostingEnvironment.IsDevelopment(); });   ConfigureWebDefaults(builder);   return builder; }

 HostBuilder：

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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()         {             IConfigurationBuilder configBuilder = new ConfigurationBuilder()                 .AddInMemoryCollection(); // Make sure there's some default storage since there are no default providers               foreach (Action<IConfigurationBuilder> 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()         {             IConfigurationBuilder configBuilder = new ConfigurationBuilder()                 .SetBasePath(_hostingEnvironment.ContentRootPath)                 .AddConfiguration(_hostConfiguration, shouldDisposeConfiguration: true);               foreach (Action<HostBuilderContext, IConfigurationBuilder> 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>(_ =>             {                 return new Internal.Host(_appServices,                     _appServices.GetRequiredService<IHostApplicationLifetime>(),                     _appServices.GetRequiredService<ILogger<Internal.Host>>(),                     _appServices.GetRequiredService<IHostLifetime>(),                     _appServices.GetRequiredService<IOptions<HostOptions>>());             });             services.AddOptions().Configure<HostOptions>(options => { options.Initialize(_hostConfiguration); });             services.AddLogging();               foreach (Action<HostBuilderContext, IServiceCollection> configureServicesAction in _configureServicesActions)             {                 configureServicesAction(_hostBuilderContext, services);             }               object containerBuilder = _serviceProviderFactory.CreateBuilder(services);               foreach (IConfigureContainerAdapter 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>();         }     }

　 Option模式

　Option 的注入

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public static IServiceCollection AddOptions(this IServiceCollection services)      {          if (services == null)          {              throw new ArgumentNullException(nameof(services));          }            services.TryAdd(ServiceDescriptor.Singleton(typeof(IOptions<>), typeof(OptionsManager<>)));          services.TryAdd(ServiceDescriptor.Scoped(typeof(IOptionsSnapshot<>), typeof(OptionsManager<>)));          services.TryAdd(ServiceDescriptor.Singleton(typeof(IOptionsMonitor<>), typeof(OptionsMonitor<>)));          services.TryAdd(ServiceDescriptor.Transient(typeof(IOptionsFactory<>), typeof(OptionsFactory<>)));          services.TryAdd(ServiceDescriptor.Singleton(typeof(IOptionsMonitorCache<>), typeof(OptionsCache<>)));          return services;      }

服务发现

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protected DbConnectionOptions Options { get; }          public DefaultConnectionStringResolver(IOptionsSnapshot<DbConnectionOptions> options)        {            Options = options.Value;        }

　　示例： IOption<>

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appsettings.json   {   "App": {     "SelfUrl": "https://localhost:44337",     "CorsOrigins": "http://localhost:4200,https://localhost:44307,https://localhost:44332"   },   "ConnectionStrings": {     "Default": "Server=localhost;Database='';Trusted_Connection=True;MultipleActiveResultSets=true"   },   "Redis": {     "Configuration": "127.0.0.1"   } }

　　解析

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public void Test()       {           var configuration = new ConfigurationBuilder()   .SetBasePath(Directory.GetCurrentDirectory())   .AddJsonFile(path: "appsettings.json", optional: false)   .Build();             var options = new ServiceCollection()               .Configure<DbConnectionOptions>(configuration)               .BuildServiceProvider()               .GetService<IOptionsSnapshot<DbConnectionOptions>>()               .Value;             Console.WriteLine(options.ConnectionStrings.Default);           Console.Read();       }   }     public class DbConnectionOptions   {       public ConnectionStrings ConnectionStrings { get; set; }         public DbConnectionOptions()       {           ConnectionStrings = new ConnectionStrings();       }   }   [Serializable]   public class ConnectionStrings : Dictionary<string, string>   {       public const string DefaultConnectionStringName = "Default";         public string Default       {           get => this.GetOrDefault(DefaultConnectionStringName);           set => this[DefaultConnectionStringName] = value;       }   }   public static class DictionaryExtensions   {       public static TValue GetOrDefault<TKey, TValue>(this Dictionary<TKey, TValue> dictionary, TKey key)       {           TValue obj;           return dictionary.TryGetValue(key, out obj) ? obj : default;       }   }