c# - Access App key data from class libraries in .NET Core / ASP.NET Core

Question

To access App Keys in a class library, do we need to do the following code in every class library and class where we need to access a AppKey?

public static IConfigurationRoot Configuration = new ConfigurationBuilder().AddJsonFile("appsettings.json").Build();

This is what I found in Microsoft docs, but this looks very redundant.

Startup class in a project as below

 public class Startup
    {
        public IConfigurationRoot Configuration { get; set; }

        public Startup()
        {
            var builder = new ConfigurationBuilder()
                .AddJsonFile("appsettings.json");

            Configuration = builder.Build();
        }

        public void ConfigureServices(IServiceCollection services)
        {
            services.AddEntityFramework().AddEntityFrameworkSqlServer()
                .AddDbContext<DbContext>(options =>
                    options.UseSqlServer(Configuration["Data:MyDb:ConnectionString"]));
        }
    }

Then how should I inject this "IConfigurationRoot" in each class of a project. And do I have to repeat this Startup class in each class Library? Why is this not part of .NET Core Framework?

Answer 1

The recommended way is to use the options pattern, provided by Microsoft and used heavily in ASP.NET Core.

Basically you create a strong typed class and configure it in the Startup.cs class.

public class MySettings 
{
    public string Value1 { get; set; }
    public string Value2 { get; set; }
}

and initialize it in the Startup class.

// load it directly from the appsettings.json "mysettings" section
services.Configure<MySettings>(Configuration.GetSection("mysettings"));

// do it manually
services.Configure<MySettings>(new MySettings 
{
    Value1 = "Some Value",
    Value2 = Configuration["somevalue:from:appsettings"]
});

then inject these options everywhere you need it.

public class MyService : IMyService
{
    private readonly MySettings settings;

    public MyService(IOptions<MySettings> mysettings) 
    {
        this.settings = mySettings.Value;
    }
}