.Net Core3.0 配置Configuration

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。

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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

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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：

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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";

输出：

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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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