Access ASP.NET Core settings during service configuration when using minimal api

Question

I am trying to access my settings in order to configure my services. I am using AWS systems manager to store my settings

// Settings class
public class Settings
{
    public string Url { get; set; }
}

// my Program.cs code
var builder = WebApplication.CreateBuilder();

// Clear default sources
builder.Configuration.Sources.Clear();

// Get configuration
builder.Configuration.AddSystemsManager(source =>
{
     source.Path = $"/{env}";
     source.ParameterProcessor = new DefaultParameterProcessor();
});
        
// Load up the settings
builder.Services.Configure<Settings>(builder.Configuration.GetSection(appName));

// Access the settings to use for configuring the services
var settings = builder.Configuration.Get<Settings>();

When I check the settings object, the values are null. However when I inject the settings into an endpoint using IOptions<Setting>, the values are populated.

I tried the .Get<Settings> after I called Build();, but that also returned null values. Is there something I am missing?

david-ao · Accepted Answer · 2023-01-26 21:26:40Z

You said you want to access the settings to configure some services. You can accomplish that with something like:

builder.Services.AddSingleton<IMyService>(x => {
    // x is IServiceProvider
    var settings = x.GetRequiredService<IOptions<Settings>>();
    var url = settings.Value.Url;
    if(url is null)
        throw new Exception("missing url");
    var myservice = new MyService(url);
    // this is the instance that will be used, use singleton/scoped/transient as needed
    return myservice;
});

where MyService is the service you want to configure, if not needed you can avoid the IMyService interface and of course you need to use the desired lifetime (singleton/scoped/transient)

Doing so though will somehow force you to explicitly declare the dependencies of "MyService".

Another way of fetching that value is:

// get the configuration section
var section = builder.Configuration.GetSection("appname:Settings");
// create the POCO
var settings = new Settings();
// bind the values to the POCO
section.Bind(settings);
// you can access the value
var yourUrl = settings.Url;
// you can still inject it as IOption<>
builder.Services.Configure<Settings>(section);

I am assuming you have an "appname" section with a "Settings" section in your configuration, if not then use .GetSection("appname"); instead of .GetSection("appname:Settings");

Jaroslav · Accepted Answer · 2023-01-23 18:21:50Z

0

According to the [docs], you should be able to retrieve your options using extension method: builder.Configuration.GetAWSOptions()

As an alternative, if you have those Settings options in appsettings.json you should be able to retrieve those using: builder.Configuration["Settings:Url"]

Also, as you have used builder.Configuration.GetSection(appName) doesn't it work for you when you try to retrieve options using: builder.Configuration.GetSection("Settings")?

edited Jan 23, 2023 at 18:21

answered Jan 23, 2023 at 18:15

Jaroslav

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