steveski / Perigee.Configuration.DependencyInjection

Perigee.Configuration.DependencyInjection

Provides a simple process for registering nested configuration types on an IServiceCollection. This is helpful when wanting dependency injection of configuration types loaded from JSON configuration.

Installation

The package can be installed from NuGet using Install-Package Perigee.Configuration.DependencyInjection

Usage

The most basic approach is when just using a single appsettings.json file for application configuration. All you need is to call the IServiceCollection extension method RegisterAppSettings. The following demonstrates registration in a .NET6.0 console application

using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using Perigee.Configuration;

var host = Host.CreateDefaultBuilder(args)
    .ConfigureServices((hostBuilderContext, services) =>
    {
        services.RegisterAppSettings<Config>();

        services.AddTransient<App>();
    })
    .Build();
    
var app = host.Services.GetRequiredService<App>();
app.Run();

If you are using appsettings override files named appsettings.<environment>.json then you can pass in the filename. Either explicitly specify the filename to use or derive the environment name from the hosting environment.

using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using Perigee.Configuration;

var host = Host.CreateDefaultBuilder(args)
    .ConfigureServices((hostBuilderContext, services) =>
    {
        // Provide environment override appsettings file
        var env = hostBuilderContext.HostingEnvironment;
        services.RegisterAppSettings<Config>($"appsettings.{env.EnvironmentName}.json");

        services.AddTransient<App>();

    })
    .Build();

var app = host.Services.GetRequiredService<App>();
app.Run();

Note that hostBuilderContext.HostingEnvironment reads an environment variable which can be set for the visual studio configuration under Properties\launchSettings.json. Either ASPNETCORE_ENVIRONMENT or DOTNET_ENVIRONMENT will be read with ASPNETCORE_ENVIRONMENT taking precedence.

{
  "profiles": {
    "ConsoleApp2": {
      "commandName": "Project",
      "environmentVariables": {
        "DOTNET_ENVIRONMENT": "Local"
      }
    }
  }
}

Because App has been registered with the IServiceCollection it can be injected with any types registered from the appsettings.json. Consider the following appsettings.json

{
  "Logging": {
    "LogLevel": {
      "Default": "Information",
      "Microsoft.AspNetCore": "Warning"
    }
  },

  "Database": {
    "ConnectionString": "prod.sqlite3",
    "SomethingElse": true
  }
}

Logging will be ignored for the purposes of service registration so to register Database as itself as well as an interface of IDatabase then the following Config class object graph should be defined.

public class Config
{
    public Database Database { get; set; }
}

public class Database : IDatabase // See comment below
{
    public string ConnectionString { get; set; }
    public bool SomethingElse { get; set; }
}

// Interface registration is entirely option and you can inject class directly
public interface IDatabase
{
    string ConnectionString { get; set; }
    bool SomethingElse { get; set; }
}

and the App class can received either the interface or class as an injected type

public class App
{
    private readonly IDatabase _databaseConfig;

    public App(IDatabase databaseConfig)
    {
        _databaseConfig = databaseConfig;
    }

    public Task Run()
    {
        Console.Write(_databaseConfig.ConnectionString);

        return Task.CompletedTask;
    }

}

Alternate scenarios

You can source json configuration fro registration from a Stream which is useful if your configuration is provided by some online service or an embedded resource, which is something you would use in a .NET MAUI application

    .
    .
    .
    .ConfigureServices((hostBuilderContext, services) =>
    {
        var a = Assembly.GetExecutingAssembly();
        using var stream = a.GetManifestResourceStream("<Name Of Executable>.appsettings.json");
        services.RegisterAppSettingsFromStream<Config>(stream);

        services.AddTransient<App>();

    })
    .
    .
    .

This project is based on Rory Primrose's work https://github.com/roryprimrose/Divergic.Configuration.Autofac but removed the dependency on AutoFac sticking with the built in Microsoft DI.