ASP.NET IConfiguration

last modified April 3, 2025

In this article, we explore the IConfiguration interface in ASP.NET 8. This interface provides access to configuration values from various sources in a unified way.

ASP.NET Core's configuration system is highly flexible and extensible. It can read configuration data from JSON files, environment variables, command-line arguments, and more.

Basic Definition

IConfiguration is the main interface for working with configuration in ASP.NET. It provides methods to read configuration values as strings, numbers, or complex objects.

The configuration system in ASP.NET Core follows a hierarchical structure. Values can be accessed using colon-separated keys that represent the hierarchy path.

IConfiguration is automatically registered in the dependency injection container. It can be injected into controllers, services, or other components that need configuration values.

ASP.NET IConfiguration Example

The following example demonstrates how to use IConfiguration in an ASP.NET 8 application.

{
  "AppSettings": {
    "Title": "Product Catalog",
    "MaxItems": 50,
    "Enabled": true,
    "ConnectionStrings": {
      "Default": "Server=localhost;Database=Products;Trusted_Connection=True;"
    }
  }
}

This JSON configuration file defines application settings with various value types. The hierarchical structure is represented through nested objects.

var builder = WebApplication.CreateBuilder(args);

// Add services to the container.
builder.Services.AddControllers();

var app = builder.Build();

app.MapControllers();
app.Run();

The default WebApplication builder automatically loads configuration from appsettings.json, environment variables, and command-line arguments.

using Microsoft.AspNetCore.Mvc;
using Microsoft.Extensions.Options;

[ApiController]
[Route("api/[controller]")]
public class ProductsController : ControllerBase
{
    private readonly IConfiguration _configuration;
    private readonly AppSettings _settings;

    public ProductsController(IConfiguration configuration, 
        IOptions<AppSettings> settings)
    {
        _configuration = configuration;
        _settings = settings.Value;
    }

    [HttpGet("config")]
    public IActionResult GetConfig()
    {
        // Direct access to configuration
        var title = _configuration["AppSettings:Title"];
        var maxItems = _configuration.GetValue<int>("AppSettings:MaxItems");
        
        // Strongly-typed access
        return Ok(new {
            ConfigTitle = title,
            ConfigMaxItems = maxItems,
            SettingsTitle = _settings.Title,
            SettingsEnabled = _settings.Enabled,
            ConnectionString = _settings.ConnectionStrings.Default
        });
    }
}

public class AppSettings
{
    public string Title { get; set; }
    public int MaxItems { get; set; }
    public bool Enabled { get; set; }
    public ConnectionStrings ConnectionStrings { get; set; }
}

public class ConnectionStrings
{
    public string Default { get; set; }
}

This controller demonstrates two ways to access configuration values. The first method uses IConfiguration directly to read values. The second uses strongly-typed configuration via IOptions.

var builder = WebApplication.CreateBuilder(args);

// Configure strongly-typed settings
builder.Services.Configure<AppSettings>(builder.Configuration.GetSection("AppSettings"));

builder.Services.AddControllers();
var app = builder.Build();

app.MapControllers();
app.Run();

The Configure method binds the AppSettings section to the AppSettings class. This enables dependency injection of strongly-typed configuration throughout the app.

The example shows both direct configuration access and the preferred strongly-typed approach. The IOptions pattern provides compile-time safety and better testability.

Source

Microsoft ASP.NET Configuration Documentation

In this article, we have explored the IConfiguration interface in ASP.NET 8. This powerful feature provides flexible access to configuration values from multiple sources.

Author

My name is Jan Bodnar, and I am a passionate programmer with extensive programming experience. I have been writing programming articles since 2007. To date, I have authored over 1,400 articles and 8 e-books. I possess more than ten years of experience in teaching programming.

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