.NET in Azure: Where and how to store application settings

While building this app I soon realized I have no clue where to store connection strings and other secrets in production.

Option 1: `appsettings.Production.json`

When I was deploying to IONOS, I had appsettings.Production.json file, containing my production database connection string, which I uploaded to IONOS manually via SFTP every time I deploy the app.

{
  "ConnectionStrings": {
    "MariaDB": "host=<>;port=<>;database=domgie;user id=<>;password=<>"
  }
}

It was never being committed to GitHub due to security. You don't want to expose it to the world.

Pros:

Easy to start with (no hassle with secrets, etc)

Cons:

Requires to be either manually uploaded, or checked-in to GitHub
Easy to lose
Will not work in CI/CD if you don't commit it to repository

Option 2: Store in App Service Secrets (Azure)

With a recent move to Azure App Service for CI/CD implementation, I had to find a different way.

Well, good news, because App Service has it all figured out for you already. So, get your connection string, and:

Locate to your App Service
In Settings tab click on Configuration
Click on New Connection string in the Connection strings table
Add your connection string and specify a name

BUT... Here is the catch

If you selected PostgreSQL type, IT WILL NOT WORK (as of today (04/07/2022)).

// Won't work if connection string type is set to PostgreSQL in App Service Configuration
var connectionString = builder.Configuration.GetConnectionString("PostgreSQL");

Why?

Azure magically adds these prefixes to all variables and dotnet parses SOME of these to magically remove the prefix.

I hear you say "This is the worst situation to be in - you parse some of the stuff, but not all of it. I HATE MAGIC!". Outrageous! I agree!

But... Let's deal with it!

Solution

Change the connection string type from PostgreSQL to Custom and let dotnet deal with it. .NET will magically remove the prefix, and the CUSTOMCONNSTR_<YOUR_CONN_NAME> will become <YOUR_CONN_NAME>. So you can use it like this:

// Works for MySQL, SQL Azure, SQL Server, Custom types
var connectionString = builder.Configuration.GetConnectionString("<YOUR_CONN_NAME>");

Option 3: Secrets and Vaults

Depending on how you deploy your application in Azure, you can also store settings as a secrets in vaults. But more on that in another blog post...

Have fun connecting!

Option 1: appsettings.Production.json