避免在ASP.NET Core Program.cs中使用静态值

Question

In my CreateWebHostBuilder() method I've added the AWS Systems Manager Parameter Store as an additional source for Configuration Builder:

public class Program
{
    public static void Main(string[] args)
    {
        CreateWebHostBuilder(args).Build().Run();
    }

    public static IWebHostBuilder CreateWebHostBuilder(string[] args)
    {
        return WebHost.CreateDefaultBuilder(args)
                  .ConfigureAppConfiguration(builder =>
                  {
                      builder.AddSystemsManager("/ConfigureStoreName/");
                  })
                  .UseStartup<Startup>();
    }
}

Instead of hardcoding "/ConfigureStoreName/ " I'd like to make this a configuration value.

When I call .ConfigureAppConfiguration() do I have access to the config values from appsettings.json that .CreateDefaultBuilder() uses? If so how would I update my code to call it? If not what is the best approach to avoid using a static value in the CreateWebHostBuilder() method?

Answer 1

Pre load setting file with that information.

If for example the setting file contained

{
  //...

  "AWS": {
    "Profile": "local-test-profile",
    "Region": "us-west-2",
    "ConfigureSource": {
      "Path": "/ConfigureStoreName/"
    }
  }

  //...
}

load that up in a configuration to extract the value.

public static IWebHostBuilder CreateWebHostBuilder(string[] args) {

    var configuration = new ConfigurationBuilder()
        .AddJsonFile("appsettings.json") //<-- or whichever file has that information
        .Build();

    string path = configuration.GetValue<string>("AWS:ConfigureSource:Path");
    //Or a strongly typed model with aws options

    return WebHost.CreateDefaultBuilder(args)
              .ConfigureAppConfiguration(builder =>
              {
                  builder.AddSystemsManager(path);
              })
              .UseStartup<Startup>();
}

Answer 2

The solution I ended up going with was to use an Environment Variable:

public class Program
{
    private static string _parameterStoreNamePath;

    public static void Main(string[] args)
    {
        _parameterStoreNamePath = Environment.GetEnvironmentVariable("AWS_PARAMETER_STORE_NAME");
        CreateWebHostBuilder(args).Build().Run();
    }

    public static IWebHostBuilder CreateWebHostBuilder(string[] args)
    {
        return WebHost.CreateDefaultBuilder(args)
                  .ConfigureAppConfiguration(builder =>
                  {
                      builder.AddSystemsManager(_parameterStoreNamePath); 
                  })
                  .UseStartup<Startup>();
    }
}

Notes:

1. In the Visual Studio project, create an Environmental Variable named AWS_PARAMETER_STORE_NAME.
2. For deployed instances, AWS_PARAMETER_STORE_NAME needs to be set in serverless.template or directly added to Lambda via the console.