[FIXED] How do I replace appsettings.json values with .env variable in docker-compose command to launch an ASP.NET Core MVC app?

Issue

I have a C# / ASP.NET Core MVC app that I have been deploying via Docker. I have been hard-coding variables in the appsetting.json file and accessing them via calls like this for example

services.Configure<ApiEndpoints>(Configuration.GetSection("ApiEndpoints"));

in my Startup.cs.

But recently I started adding variables for deploying into a .env file and deploying like this docker-compose --env-file .env up. But I can't access the variables in my .env file in the .NET app.

For example I tried this

Console.WriteLine(Configuration.GetSection("APPSETTINGS_DB_STR"));

in Startup.cs where in the .env file I added this variable APPSETTINGS_DB_STR=isThisLoggingCorrectly and it logged as

amaranth_main               | Microsoft.Extensions.Configuration.ConfigurationSection

in my console... So how do I get the asp.net to access the docker .env variable?

This is my docker-compose.yml

version: '3.8'

volumes:
  data:

services:
  postgresql_MENTIONvlt_bg:
    image: postgres
    # explicit container name
    container_name: postgresql_vlt_bg
    environment:
      - POSTGRES_USER=${POSTGRES_USER}
      - POSTGRES_PASSWORD=${POSTGRES_PASSWORD}
      - POSTGRES_DB=${POSTGRES_DB}
    ports:
      - 5432:5432
    volumes:
      - data:/var/lib/postgresql_vlt_bg
  amaranth_main:
    container_name: amaranth_main
    links:
      - postgresql_MENTIONvlt_bg
    depends_on:
      - postgresql_MENTIONvlt_bg
    build:
      context: .
      dockerfile: Dockerfile
    ports:
      - 8000:5000
      - 8001:5001
    environment:
      - ASPNETCORE_ENVIRONMENT=Release
      - ASPNETCORE_Kestrel__Certificates__Default__Password=${Kestrel_Cert_Password}
      - ASPNETCORE_Kestrel__Certificates__Default__Path=${Kestrel_Cert_Rel_Path}
      - APPSETTINGS_DB_STR=${APPSETTINGS_DB_STR}
    volumes:
      - ${Kestrel_Cert_Abs_Path}:/https:ro

P.S. POSTGRES_USER, POSTGRES_PASSWORD, and POSTGRES_DB are being passed through just fine.

Solution

The fix was to first make APPSETTINGS_DB_STR into APPSETTINGS__DB__STR. Then I had to access the variable like this in my c# app code. Environment.GetEnvironmentVariable(“APPSETTINGS__DB__STR”)

Answered By - ChristianOConnor

Answer Checked By - Terry (PHPFixing Volunteer)