Override an array in azure app service application settings

Question

In my .NET Core application, I added an array to the appsettings.json, which looks like this:

{
  "SettingsA": {
    "PropA": [
        "ChildObjectA": {
          ...
        },
        "ChildObjectB": {
          ...
        }
    ]
  }
}

If I would like to override that value from Application Settings in my azure app service, so that it will have empty array:

{
  "SettingsA": {
    "PropA": []
  }
}

Is there a way to do this?

I tried to put

SettingsA:PropsA  ->  []

In the application settings, but it doesn't seem to override the value of appsettings.json

Answer 1

Just to top up all the great answers already given here, here is how we did it in our real life scenario.

We needed a collection of supported languages to be configured in our app settings. Here is how it looked in the appSettings.json in our .NET Core project:

{
    ...

    "SupportedLanguages": [
        {
            "Code": "en-AU",
            "Name": "English (Australia)"
        },
        {
            "Code": "en-GB",
            "Name": "English (United Kingdom)"
        },
        {
            "Code": "en-US",
            "Name": "English (United States)"
        }
    ]
}

And this is how it ended up looking in our Azure App Service:

It's a bit fiddly, especially if you have a larger or more complex hierarchy, but I don't think there's another way for now.

Answer 2

The answer here https://www.ryansouthgate.com/2016/03/23/iconfiguration-in-netcore/ is that you can override elements within an array or add additional elements but he says that you can't override the entire array, which seems strange.

Syntax for overriding uses zero-based access such as SettingsA:PropA:0:Something and I have tried this on App Services and can confirm it works.

Answer 3

You could use AddEnvironmentVariables property to achieve override appsettings on azure to local settings.

First configure the setting in portal:

Note: The value here is null.

To override nested keys in the App Settings section we can define a variable using the full path SettingsA:PropA as name or using double underscore SettingsA__PropA. You could refer to this article.

In local, you could configure as below: In Startup.cs:

public Startup(IHostingEnvironment env)
        {
            var builder = new ConfigurationBuilder()
                .SetBasePath(env.ContentRootPath)
                .AddJsonFile("appsettings.json", optional: false, reloadOnChange: true)
                .AddJsonFile($"appsettings.{env.EnvironmentName}.json", optional: true)
                .AddEnvironmentVariables();
            configuration = builder.Build();
        }
        public IConfiguration configuration { get; }

        // This method gets called by the runtime. Use this method to add services to the container.
        public void ConfigureServices(IServiceCollection services)
        {
            services.AddMvc();
            services.AddOptions();
            services.Configure<SettingsOptions>(configuration.GetSection("SettingsA"));

        }

In appsettings.json:

{"SettingsA": {
    "PropA": ["a","b"]
    }
}

In HomeController:

private readonly IOptions<SettingsOptions> options;
        public HomeController(IOptions<SettingsOptions> options)
        {
            this.options = options;
        }

        public IActionResult Index()
        {
            var value = options.Value;
            ViewBag.Index = value.PropA+"success";
            return View();
        }

In SettingsOption:

public class SettingsOptions
    {
        public string SettingsA { get; set; }
        public string PropA { get; set; }
    }

After you publish the project to azure, it will override the PropA value. For more details about how to read appsetting from asp.net core, please follow this case.