Specify boolean variable using environment variables in .NET Core

Question

Given the following program:

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

        public static IWebHostBuilder CreateWebHostBuilder(string[] args) =>
            WebHost.CreateDefaultBuilder(args)
                .ConfigureAppConfiguration((builderContext, config) =>
                {
                    var env = builderContext.HostingEnvironment;
                    config.AddJsonFile("appsettings.json", optional: false, reloadOnChange: true)
                        .AddJsonFile($"appsettings.{env.EnvironmentName}.json", optional: true, reloadOnChange: true)
                        .AddEnvironmentVariables(prefix: "Prefix_");
                })
                .UseStartup<Startup>();
    }

and a configuration usually defined in appsettings.json as:

{
    "SomeSection": {
        "SomeOption": true
    }
}

is there a way to override it as environment variable (using the method specified in the docs)?

---

I've tried with (I'm on macOS, but the same problem also happens in Linux and Docker Compose):

export Prefix_SomeSection__SomeOption=true

but it's parsed as a string and it can't convert it to a boolean. The same method works with every other non boolean option, which seems to imply that there's some undocumented way to define a variable as a boolean.

Answer 1

I was setting the environment variables with docker-compose.yml like this:

version: '3.4'

services:

  server:
    environment:
      Prefix_SomeSection__SomeOption: true

the error that I got was related to docker-compose.yml, not .NET Core, and it was:

contains true, which is an invalid type, it should be a string, number, or a null

The solution is to just wrap that true into a string like this:

version: '3.4'

services:

  server:
    environment:
      Prefix_SomeSection__SomeOption: "true"