新的 Visual Studio 2019 中的环境变量为空，但 Visual Studio 2017 中的环境变量为空

Question

I downloaded and setup the newly released Visual Studio 2019 Professional and opened a solution I have been working on in Visual Studio 2017 Professional.

This solution contains 3 ASP.NET Core projects and 1 docker-compose project.

When starting debug session in 2019 I get a null reference exception on one line where I'm referring to my docker-compose environment variables.

However if I open the same solution in Visual Studio 2017 I don't get this null reference exception as the values are correctly read from the docker-compose.yml file.

I have looked over the setup of both versions of Visual Studio and don't appear to be missing anything.

// Create intance of item message handler
var container = services.BuildServiceProvider();
var _settings = container.GetService<IOptions<Settings>>().Value;

var itemListenerSettings = _settings.RabbitSettings.ListenerSettings.FirstOrDefault(s => s.Key == "ItemListener");
if (itemListenerSettings.Value != null)
{
  // Register item listener...
}

version: '3.4'

services:
  microserviceapi:
    image: microserviceapi
    container_name: ms
    build:
      context: ./MicroserviceApi
      dockerfile: Dockerfile
    environment:
      RabbitSettings:Hostname: "rabbit"
      RabbitSettings:Username: "user"
      RabbitSettings:Password: "pass"
      RabbitSettings:ReconnectionRetries: "10"
      RabbitSettings:ReconnectionTime: "1000"
      RabbitSettings:ListenerSettings__ItemListener__ExchangeName: "Imagine.ItemManagement"
      RabbitSettings:ListenerSettings__ItemListener__ExchangeType: "topic"
      RabbitSettings:ListenerSettings__ItemListener__QueueName: "foo.Item"
      RabbitSettings:ListenerSettings__ItemListener__RoutingKey: "item.*"

While running a debug session in Visual Studio 2019, calling var _settings = container.GetService<IOptions<Settings>>().Value I expect the property RabbitSettings of the variable _settings to contain the values from my docker-compose.yml file as it does in Visual Studio 2017.

Answer 1

The environment variables contain the ':' characters. As documented here:

https://docs.microsoft.com/en-us/aspnet/core/fundamentals/configuration/?view=aspnetcore-2.2#environment-variables-configuration-provider

... it's recommended to use double-underscore '__' instead of ':' in enviroment variable names in asp.net core. ':' works fine in VS 2017 solutions, but VS2019 needs double-underscore '__'.