Dockerized .NET Project - handling DB migrations

Question

I have dockerized API & PostgreSQL database, when I locally execute

dotnet ef migrations add InitialCreate -p MyProject1 -s MyProject2

It successfully creates initial migration.

When I try to update DB via

dotnet ef database update -p MyProject1 -s MyProject2

I get error, because it cannot communicate with Docker and it tries to update it locally (I assume) - error message:

...The ConnectionString property has not been initialized.

However, in both of my appsettings.json I have ConnectionStrings: "" just empty, and use environment variables:

services:
  
  api:
    build:
      context: ../../                
      dockerfile: environments/dev/Dockerfile
    ports:
      - "5000:5000"
    environment:
      - ConnectionStrings__DefaultConnection=User ID=${POSTGRES_USER};Password=${POSTGRES_PASSWORD};Server=${POSTGRES_SERVER};Port=${POSTGRES_PORT};Database=${POSTGRES_DB};
      - ASPNETCORE_URLS=http://+:5000
      - ASPNETCORE_ENVIRONMENT=Development
      - DOTNET_USE_POLLING_FILE_WATCHER=1
    volumes:
      - ../../:/src
    working_dir: /src/API
    env_file:
      - ../../.env
    depends_on:
      - db
    restart: always
    command: dotnet watch --no-hot-reload --project API.csproj run --urls=http://0.0.0.0:5000

  db:
    image: postgres:latest
    environment:
      - POSTGRES_DB=${POSTGRES_DB}
      - POSTGRES_USER=${POSTGRES_USER}
      - POSTGRES_PASSWORD=${POSTGRES_PASSWORD}
    ports:
      - "5432:5432"
    restart: always
    env_file:
      - ../../.env
    volumes:
      - app_data:/var/lib/postgresql/data
        
volumes:
  app_data:

How to handle migrations when using dockerized PostgreSQL?

Giorgio Todeschini · Accepted Answer · 2025-08-28 13:56:37Z

0

It's not clear if the API application and the DB are in the same container, or if you're using a shell inside the container.

I assume you're invoking the dotnet ef command from your development machine, not from within a container.

A solution would be to generate a SQL script instead of updating the database directly using the following command:

bashdotnet ef migrations script -p MyProject1 -s MyProject2 -o initial-create.sql

Once the initial-create.sql file is generated, you can apply it to the database using the psql CLI or a tool like DBeaver.

answered Aug 28 at 13:56

Giorgio Todeschini

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