I’ve been playing recently with ASP.Net Core and I’m developing a small Web API project in order to teach myself the framework.

In still article I’ll explain how to use a Postgres database with Docker, in order to make your development experience much more enjoyable.

Before moving on, please make sure that you’ve installed:

• Docker
• Docker-Compose

First, create the docker-compose.yml file in your root directory of the project, the file should contain:

version: '3.4'
services:
  postgres:
    image: postgres
    environment:
      - POSTGRES_USER=app
      - POSTGRES_PASSWORD=app
      - POSTGRES_DB=mydbname
    volumes:
      - ./volumes/data/db:/var/lib/postgresql/data
    ports:
       - 5432:5432

This specific postgres configuration passes some self-explanatory environments variables to the postgres database, it binds the ./volumes/data directory to the postgres’ data volume and it exposes the port 5432. We bind the volume so we can achieve data persistency and explore the files generated by the postgres database.

Next, add the following packages to your ASP.Net Core application:

  dotnet add package Npgsql.EntityFrameworkCore.PostgreSQL
  dotnet add package Npgsql.EntityFrameworkCore.PostgreSQL.Design

Add your database connection configuration to the appsettings.Development.json file, note that they match the strings from the docker-compose.yml file. When running in production you should deploy each service in a separate container and configure them with environment variables. Never hardcode sensitive information in your files!

{
"DatabaseConfig": {
    "PostgresSQL": "Server=localhost;Port=5432;Database=mydbname;User Id=app;Password=app;"
  },
...
}

Now in the Startup.cs file, when configuring the application context, specify that you want to use PostgresSQL.

services.AddDbContext<ApplicationContext>(options =>
{
    options.UseNpgsql(Configuration.GetSection("DatabaseConfig")["PostgresSQL"]);
});

This is it! Make sure that your application is not running and start the database with docker-compose up. After the database has started open a new terminal and add the migrations:

dotnet ef migrations add InitialMigration
dotnet ef database update

If you’d like to stop the database you can run docker ps and docker stop <hash> where <hash> is the hash of your database container. Following the steps from above gives you an isolated development database that you can use alongside your ASP.Net Core application, if you need to add ElasticSearch, Redis or another service all you need to do is change the docker-compose.yml file to include them and voilà.

Thank you for reading, have a nice day!