?準備

.NET core和.NET項目配置上有了很大的改變，支持的也更加豐富了比如命令行，環境變量，內存中.NET對象，設置文件等等。.NET項目我們常常把配置信息放到webConfig 或者appConfig中。配置相關的源碼https://github.com/aspnet/Extensions；如果打開源碼項目?如果遇到以下錯誤，未遇到直接跳過。

錯誤提示：?error : The project file cannot be opened by the project system, because it is missing some critical imports or the referenced SDK cannot be found. Detailed Information:

解決辦法：查看本地安裝的sdk 與 global.json中制定的版本是否一致：然后修改即可

開始

新建個Asp.net Core web應用程序系統默認創建了appsettings.json ；在應用啟動生成主機時調用CreateDefaultBuilder方法，默認會加載appsettings.json。代碼如下： 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); } }利用?GetValue，GetSection，GetChildren讀取appsettings.json 鍵值對 。我們打開appsettings.json文件：

將文件讀入配置時，會創建一下唯一的分層健來保存配置值：

• Logging:LogLevel:Default

• Logging:LogLevel:System

• Logging:LogLevel:Microsoft

• Logging:LogLevel:Microsoft.Hosting.Lifetime

• AllowedHosts

var jsonValue = $"AllowedHosts:{_config["AllowedHosts"]}"+ "\r\n"; jsonValue += "Logging:LogLevel:Default：" + _config.GetValue<string>("Logging:LogLevel:Default")+ "\r\n"; //GetSection 返回IConfigurationSection；如果未匹配到 返回null //jsonValue += "---" + _config.GetSection("Logging:LogLevel:System"); jsonValue += "Logging:LogLevel:System：" + _config.GetSection("Logging:LogLevel:System").Value+ "\r\n\n"; var logSection = _config.GetSection("Logging:LogLevel"); var configurationSections = logSection.GetChildren(); foreach (var sections in configurationSections) { jsonValue += $"{sections.Path}:{sections.Value}"; jsonValue += "\r\n"; } jsonValue += "\r\n";

輸出：

?

配置指定json文件綁定至類

新建一個json文件-AAAppSettings.json{ "AA": { "RabbitMqHostUrl": "rabbitmq://localhost:5672", "RabbitMqHostName": "localhost", "RabbitMqUserName": "admin", "RabbitMqPassword": "123" } } 使用ConfigureAppConfiguration方法配置指定的json文件public static IHostBuilder CreateHostBuilder(string[] args) => Host.CreateDefaultBuilder(args) .ConfigureAppConfiguration((hostingContext, config) => { config.SetBasePath(Directory.GetCurrentDirectory()); config.AddJsonFile("AAAppSettings.json", optional: true, reloadOnChange: true); })

使用bind方法綁定到新建的類上如：? ?

public partial class AAConfig { public string RabbitMqHostUrl { get; set; } public string RabbitMqHostName { get; set; } public string RabbitMqUserName { get; set; } public string RabbitMqPassword { get; set; } }

? ??

var aaConfig = new AAConfig(); _config.GetSection("AA").Bind(aaConfig); jsonValue += aaConfig.RabbitMqHostUrl + "\r\n"; jsonValue += aaConfig.RabbitMqHostName + "\r\n"; jsonValue += aaConfig.RabbitMqUserName + "\r\n"; jsonValue += aaConfig.RabbitMqPassword + "\r\n"; return jsonValue;

運行輸出：

總結

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