Is services.AddSingleton<IConfiguration> really needed in .net core 2 API

Question

I accessed appsettings.json In .NET Core 2 Web API Controller simply by adding below:

public class MyController : Controller
    {
        private readonly IConfiguration appConfig;

        public MyController(IConfiguration configuration)
        {
            appConfig = configuration;
        }
    }

Without adding below in Startup class ConfigureServices(IServiceCollection services) after services.AddMvc();:

services.AddSingleton<IConfiguration>(Configuration);

Is there any flaws in my approach? In official docs for .Net Core 2 configuration section, its not mentioned to use 'AddSingleton' not even once: https://learn.microsoft.com/en-us/aspnet/core/fundamentals/configuration

also by searching I couldn't find related content with accessing configuration! https://learn.microsoft.com/en-us/search/index?search=AddSingleton&scope=ASP.NET+Core

Links below shows AddSingleton as if mandatory step:

Access appsettings.json values in controller classes

https://blogs.technet.microsoft.com/dariuszporowski/tip-of-the-week-how-to-access-configuration-from-controller-in-asp-net-core-2-0/

Federico Dipuma · Accepted Answer · 2017-10-04 21:50:12Z

22

As the official roadmap for ASP.NET Core 2.0 says:

An IConfiguration instance will be added to the services container by default in ASP.NET Core 2.0, so that all applications can easily retrieve configuration values via the container

So services.AddSingleton<IConfiguration> (or similar) is already called by the framework itself.

You may see this behavior inside WebHostBuilder.cs file or (when using the utility extension methods) inside HostBuilder.cs file.

edited Oct 4, 2017 at 21:50

answered Oct 4, 2017 at 21:36

Federico Dipuma

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3 Comments

Jawad Al Shaikh Over a year ago

So what happens when user adding it manually beside its being set by default? it seems no warns or errors appeared!

Federico Dipuma Over a year ago

As with any other registration in ASP.NET Core DI, the last registration is used whenever anyone requests that service from the IServiceProvider. Because, in your case, the registration is the same, nothing changes (you have now two identical registrations for the same service).

Died Over a year ago

On VS2022 preview 4.1, builder.Services.AddSingleton<IConfiguration>(builder.Configuration); will cause System.StackOverflowException. So this line should be remove.

Ozmen · Accepted Answer · 2019-07-02 09:11:22Z

0

I am not sure if it is needed.But we have appsettings.local.json and if we do not add this in program.cs, we can not read datas from appsetting.local.json. so In program.cs we add ConfigureServices statament in CreateWebHostBuilder method at program.cs

var webHostBuilder = WebHost.CreateDefaultBuilder(args)
                    .UseApplicationInsights()
                    .ConfigureServices(services => services.AddSingleton<IConfiguration>(config))
                    .UseStartup<Startup>();

answered Jul 2, 2019 at 9:11

Ozmen

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1 Comment

GvSharma Over a year ago

AddSingleton is not accessible

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