C#•3y ago

❔ ASP.NET Core Environment Variables in Dependency Injection

Hello, I have a (probably) slightly dumb question.
What's the correct/recommended way to inject an environment variable (like from docker-compose or similar) into a service class in ASP.NET Core?
Googling somehow always points me toward "multiple environments" such as test/staging/prod, but that's not what I'm looking for.
My hunch is that I'm supposed to do it in

Program.cs

Program.cs

when setting up DI, somehow.

In Spring I might do something like this to inject

MY_ENV_VAR

MY_ENV_VAR

as a

String

String

into

MyService

MyService

@Service
class MyService(@Value("${MY_ENV_VAR}") val myEnvVar: String) { ... }

@Service
class MyService(@Value("${MY_ENV_VAR}") val myEnvVar: String) { ... }

mindhardt•7/30/23, 1:00 PM

I guess you are heading in the wrong direction

mindhardt•7/30/23, 1:01 PM

You need it as a configuration?

phaseshift•7/30/23, 1:01 PM

Anything in environment can be read through the IConfiguration

mindhardt•7/30/23, 1:01 PM

Then you would need Microsoft.Extensions.Configuration

mindhardt•7/30/23, 1:01 PM

And you can inhect either a strongly-typed binded Options object or directly IConfiguration

phaseshift•7/30/23, 1:02 PM

IOptions, yes

mindhardt•7/30/23, 1:03 PM

Thx for correcting blobthumbsup

CottonOP•7/30/23, 1:05 PM

Yeah, I ended up with something like this

Which is then defined in appsettings.Development.json

CottonOP•7/30/23, 1:06 PM

although I haven't yet tested if actual OS environment variables would affect this at all

mindhardt•7/30/23, 1:28 PM

Depends on your configuration setup, if you do something like .AddJsonFile().AddEnvironmentVariables() or use default host builder then you are probably fine

mindhardt•7/30/23, 1:29 PM

You can add env vars in your IDE to test things