Access Azure App Service ConnectionString from ASP.NET Core

Question

I've got an azure app service that I've set up like this:

But when I call IConfiguration.GetConnectionString("db") I get null back.

I've read articles like this https://mderriey.com/2018/08/21/azure-app-service-connection-strings-and-asp-net-core/ which say "it just works", but they're all several years old. I assume something's changed, but what?

Enumerating over all settings in my IConfiguration object I've got no connection strings. I do in development, where my appsettings.development.json has a connectionStrings: { db: "" } defined.

I can see and read the ENV variable: POSTGRESQLCONNSTR_db from within code, and it's value is correct (what I've set via the Azure portal).

Should I expect to be able to do IConfiguration.GetConnectionString("db")? Or am I expected to switch between reading env variables in prod vs dev.

Do I need to include some nuget package to make IConfiguration work under Azure with these ENV variables and their mad prefixes?

My startup.cs basically looks like:


        public Startup(IConfiguration configuration)
        {
            this.Configuration = configuration;
        }

        public IConfiguration Configuration { get; }

Nothing else in there of interest to this question.

dotsa · Accepted Answer · 2022-02-23 19:00:31Z

5

I got confused as well, so here it is:

You have two options to specify Connection String locally:

launchSettings.json (environmentVariables section)

  "environmentVariables": {
     "ASPNETCORE_ENVIRONMENT": "Development",
     "SQLAZURECONNSTR_SomeConnectionString": "DefaultEndpointsProtocol=blah"
   }

appSettings.json

  "ConnectionStrings": {
    "SomeConnectionString": "DefaultEndpointsProtocol=blah"
  }

Having either way will allow you to get the connection string setting by calling:

IConfiguration.GetConnectionString("SomeConnectionString")

Function call above will also work when deployed to Azure, as it is using EnvironmentVariables configuration provider to read settings.

edited Feb 23, 2022 at 19:00

answered Feb 18, 2022 at 22:37

dotsa

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Comments

Kirk Larkin · Accepted Answer · 2020-06-04 15:44:23Z

4

The POSTGRESQLCONNSTR_ prefix isn't supported by the environment variables configuration provider. The docs shows this, in an indirect fashion, where it states that the following prefixes are supported:

CUSTOMCONNSTR_

MYSQLCONNSTR_

SQLAZURECONNSTR_

SQLCONNSTR_

It's also apparent in the source code for the provider.

There are a couple of options for working around this:

Change the Type to Custom in the Connection strings section of the Azure portal.
Change to an Application setting of ConectionStrings:db in the Azure portal.

This is being tracked on GitHub: https://github.com/dotnet/runtime/issues/36123.

answered Jun 4, 2020 at 15:44

Kirk Larkin

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Comments

joakimja · Accepted Answer · 2020-06-03 14:08:56Z

1

Instead of getting the config from the interface

IConfiguration.GetConnectionString("db")

try to get it from

Configuration.GetConnectionString("db")

And in production you have an empty string in production.appsetting.json and add the value in azure(appservice) configuration directly under connectionstrings(this will override the json setting file). And no nugets are needed for reading from appsettings

answered Jun 3, 2020 at 14:08

joakimja

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3 Comments

Andrew Bullock Over a year ago

Yes, thanks, I was simply showing the type of IConfiguration for the purpose of asking a question, otherwise it wouldn't compile. As for your 2nd tip, thats what I've done, that's what the question asks.

Andrew Bullock Over a year ago

sorry, are you saying you need a placeholder connection string key in the production json in order for it to be overridden? Or will (should) it get set regardless. I have no connectionstring keys in my prod json

joakimja Over a year ago

yes there need to be an placeholder. The value can be what ever it will be replaced ie "SetInAzure"

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