1.3 落地实践及多环境调试

新建项目

新建ASP.NET Core Web 应用程序

Configuration加载顺序

namespace Microsoft.Extensions.Hosting
{
    //
    // 摘要:
    //     Provides convenience methods for creating instances of Microsoft.Extensions.Hosting.IHostBuilder
    //     with pre-configured defaults.
    public static class Host
    {
        //
        // 摘要:
        //     Initializes a new instance of the Microsoft.Extensions.Hosting.HostBuilder class
        //     with pre-configured defaults.
        //
        // 返回结果:
        //     The initialized Microsoft.Extensions.Hosting.IHostBuilder.
        //
        // 言论：
        //     The following defaults are applied to the returned Microsoft.Extensions.Hosting.HostBuilder:
        //     • set the Microsoft.Extensions.Hosting.IHostEnvironment.ContentRootPath to the
        //     result of System.IO.Directory.GetCurrentDirectory
        //     • load host Microsoft.Extensions.Configuration.IConfiguration from "DOTNET_"
        //     prefixed environment variables
        //     • load app Microsoft.Extensions.Configuration.IConfiguration from 'appsettings.json'
        //     and 'appsettings.[Microsoft.Extensions.Hosting.IHostEnvironment.EnvironmentName].json'
        //     • load app Microsoft.Extensions.Configuration.IConfiguration from User Secrets
        //     when Microsoft.Extensions.Hosting.IHostEnvironment.EnvironmentName is 'Development'
        //     using the entry assembly
        //     • load app Microsoft.Extensions.Configuration.IConfiguration from environment
        //     variables
        //     • configure the Microsoft.Extensions.Logging.ILoggerFactory to log to the console,
        //     debug, and event source output
        //     • enables scope validation on the dependency injection container when Microsoft.Extensions.Hosting.IHostEnvironment.EnvironmentName
        //     is 'Development'
        public static IHostBuilder CreateDefaultBuilder();
        //
        // 摘要:
        //     Initializes a new instance of the Microsoft.Extensions.Hosting.HostBuilder class
        //     with pre-configured defaults.
        //
        // 参数:
        //   args:
        //     The command line args.
        //
        // 返回结果:
        //     The initialized Microsoft.Extensions.Hosting.IHostBuilder.
        //
        // 言论：
        //     The following defaults are applied to the returned Microsoft.Extensions.Hosting.HostBuilder:
        //     • set the Microsoft.Extensions.Hosting.IHostEnvironment.ContentRootPath to the
        //     result of System.IO.Directory.GetCurrentDirectory
        //     • load host Microsoft.Extensions.Configuration.IConfiguration from "DOTNET_"
        //     prefixed environment variables
        //     • load host Microsoft.Extensions.Configuration.IConfiguration from supplied command
        //     line args
        //     • load app Microsoft.Extensions.Configuration.IConfiguration from 'appsettings.json'
        //     and 'appsettings.[Microsoft.Extensions.Hosting.IHostEnvironment.EnvironmentName].json'
        //     • load app Microsoft.Extensions.Configuration.IConfiguration from User Secrets
        //     when Microsoft.Extensions.Hosting.IHostEnvironment.EnvironmentName is 'Development'
        //     using the entry assembly
        //     • load app Microsoft.Extensions.Configuration.IConfiguration from environment
        //     variables
        //     • load app Microsoft.Extensions.Configuration.IConfiguration from supplied command
        //     line args
        //     • configure the Microsoft.Extensions.Logging.ILoggerFactory to log to the console,
        //     debug, and event source output
        //     • enables scope validation on the dependency injection container when Microsoft.Extensions.Hosting.IHostEnvironment.EnvironmentName
        //     is 'Development'
        public static IHostBuilder CreateDefaultBuilder(string[] args);
    }
}

注意这段注释

    //     • load app Microsoft.Extensions.Configuration.IConfiguration from 'appsettings.json'
    //     and 'appsettings.[Microsoft.Extensions.Hosting.IHostEnvironment.EnvironmentName].json'
    //     • load app Microsoft.Extensions.Configuration.IConfiguration from User Secrets

```csharp
public static class Program
    {
        public static void Main(string[] args)
        {
            CreateHostBuilder(args).Build().Run();
        }
        public static IHostBuilder CreateHostBuilder(string[] args) =>
            Host.CreateDefaultBuilder(args)
                .ConfigureWebHostDefaults(webBuilder =>
                {
                    webBuilder.UseStartup<Startup>();
                });
    }

就是说Host.CreateDefaultBuilder()加载Configuration的顺序是

1. appsettings.json
2. appsettings.{envName}.json
3. usesecrets(secrets.json)

同一个节点信息如果在三个.json文件中都有定义，会依赖加载顺序，最后的会覆盖之前的

多环境配置

这里的设计思路是将全局通用配置放在`appsettings.json中，不同环境根据需求配置自己的节点，也可以使用相同名称来覆盖appsettings.json

appsettings.json

{
  "Logging": {
    "LogLevel": {
      "Default": "Information"
    }
  },
  "AllowedHosts": "*"
}

appsettings.Development.json

{
  "ConnectString": "Server=.;Database=WebApp01.Db.Dev;uid=sa;pwd=wpl19950815;"
}

appsettings.Sit.json

{
  "ConnectString": "Server=.;Database=WebApp01.Db.Sit;uid=sa;pwd=wpl19950815;"
}

调试不同环境

通过设置 environmentVariables:ASPNETCORE_ENVIRONMENT环境名称来切换使用不同环境的配置文件，这里环境变量名称需要和appsetting.{envName}.json中{envName}保持一致