准备

.NET core和.NET项目配置上有了很大的改变，支持的也更加丰富了比如命令行，环境变量，内存中.NET对象，设置文件等等。.NET项目我们常常把配置信息放到webConfig 或者appConfig中。配置相关的源码https://github.com/aspnet/Extensions；如果打开源码项目如果遇到以下错误，未遇到直接跳过。

错误提示：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:

解决办法：查看本地安装的sdk 与 global.json中制定的版本是否一致：然后修改即可

开始

新建个Asp.net Core web应用程序系统默认创建了appsettings.json ；在应用启动生成主机时调用CreateDefaultBuilder方法，默认会加载appsettings.json。代码如下：

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读取appsettings.json 键值对 。我们打开appsettings.json文件：

将文件读入配置时，会创建一下唯一的分层健来保存配置值：

• 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";

配置指定json文件绑定至类

新建一个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方法绑定到新建的类上如：

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;

运行输出：

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