如何在 dotnet 应用中使用 Azure 应用服务的应用设置？

Question

Since i started working with Azure and the App Service resource, there has been a question that i would like to have a clear answer regarding the app settings configuration variables.

Looking into the documentation here , we can see the following:

"In App Service, you can set app settings and connection strings outside of your app code. Then you can access them in any class using the standard ASP.NET pattern:

using System.Configuration;
...
// Get an app setting
ConfigurationManager.AppSettings["MySetting"];
// Get a connection string
ConfigurationManager.ConnectionStrings["MyConnection"];
}

If you configure an app setting with the same name in App Service and in web.config, the App Service value takes precedence over the web.config value. The local web.config value lets you debug the app locally, but the App Service value lets your run the app in product with production settings. Connection strings work in the same way. This way, you can keep your application secrets outside of your code repository and access the appropriate values without changing your code."

Does this mean, that ConfigurationManager is the class responsible for the magic of using app service configuration variables if they exist?

If we use for example

    var builder = new ConfigurationBuilder()
        .SetBasePath(Directory.GetCurrentDirectory())
        .AddJsonFile($"appsettings.json", true, true)

Since ConfigurationBuilder does not use, in this case, environment variables i supose the App service variables will not work anymore am i right?

In the example above, it's dotnet core and i looked into the documentation here and the way to configure seems to be a bit different. I wonder if a .AddEnvironmentVariables(); is required to the configuration builder.

Looking into the documentation its hard to understand if its a matter of the application being configured to add environment variables or if the App Service has the capability to inject app settings in the app configuration. If we look here . We see this:

How will the variables with that prefix be treated?

For example, is it different having a variable in the configuration app settings with or without APPSETTING_ prefix?

  {
    "name": "Test",
    "value": "123",
    "slotSetting": false
  }

and

  {
    "name": "APPSETTING_Test",
    "value": "123",
    "slotSetting": false
  }

Answer 1

Yes, if you .AddEnvironmentVariables() the AppSettings as configured in AppService will be included in your builder, but certain prefixes are preferable such as ASPNETCORE_

https://docs.microsoft.com/en-us/aspnet/core/fundamentals/configuration/?view=aspnetcore-6.0#default-host-configuration-sources