docker compose environment variable to IConfiguration, how to do?

Question

I am using docker compose file to keep all the environment variables,

environment:
  - Instance=https://login.microsoftonline.com/
  - ClientId=xxxxxxxx

and I can access these variables in my asp.net core web api app statrtup class like below,

var instance = Environment.GetEnvironmentVariable("Instance")
var clientId = Environment.GetEnvironmentVariable("ClientId")

In statrtup class I can send the entire like below IConfiguration to some method like,

services.AddProtectedWebApi(Configuration);

where it will automatically read all the configuration what I have configured in AzureAd section of appsettings.json

"AzureAd": {
"Instance": "https://login.microsoftonline.com/",
"ClientId": "xxxxxxxxxxxxxxxxxxxxxx",
"Domain": "xxxxxxxxxxxxxxxxxxxxxxxxx",
"TenantId": "xxxxxxxxxxxxxxxxxxxxxxx"

},

Now my question is, how we can read environment variables (instead of appsettings.json ) and prepare IConfiguration with config section AzureAd ?

Answer 1

You should use the following environment variable names with prefix:

environment:
- AzureAd__Instance=https://login.microsoftonline.com/
- AzureAd__ClientId=xxxxxxxx

to override appsettings.json