Configuration and Options Pattern

45 min

ASP.NET Core provides a flexible configuration system that can read from multiple sources (JSON files, environment variables, command-line arguments, user secrets, Azure Key Vault, etc.), enabling different configurations for different environments. Configuration is hierarchical—later sources override earlier ones. This enables environment-specific settings without code changes. Understanding configuration enables flexible application deployment. Configuration is essential for production applications.

The Options pattern allows you to bind configuration sections to strongly-typed objects, providing type-safe access to configuration values. Instead of accessing configuration with string keys, you create classes that represent configuration sections and bind them. This provides IntelliSense, compile-time checking, and better maintainability. Understanding the Options pattern enables professional configuration management. The Options pattern is the recommended approach.

You can use configuration providers for JSON files (appsettings.json), environment variables, command-line arguments, and more, enabling flexible configuration sources. JSON files are common for default settings. Environment variables override JSON for environment-specific values. Command-line arguments provide runtime overrides. Understanding configuration providers enables flexible configuration. Multiple providers enable layered configuration.

IOptions<T>, IOptionsSnapshot<T>, and IOptionsMonitor<T> provide different ways to access options with different update behaviors. IOptions<T> reads configuration once at startup. IOptionsSnapshot<T> reads configuration per request (supports reloading). IOptionsMonitor<T> supports change notifications. Understanding these interfaces enables choosing appropriate options access. Different interfaces suit different scenarios.

Configuration best practices include using strongly-typed options, storing secrets securely (not in code), using environment-specific configuration files, and validating configuration. Understanding best practices enables secure, maintainable configuration. Configuration management is critical for production applications.

Best practices include using the Options pattern for type-safe configuration, storing secrets in secure storage (Azure Key Vault, user secrets), using environment variables for deployment-specific values, and validating configuration on startup. Understanding configuration enables flexible, secure application deployment. Configuration is fundamental to application management.

Key Concepts

ASP.NET Core provides flexible configuration from multiple sources.
The Options pattern binds configuration to strongly-typed objects.
Configuration providers support JSON, environment variables, and more.
IOptions, IOptionsSnapshot, and IOptionsMonitor provide different access patterns.
Configuration is hierarchical—later sources override earlier ones.

Learning Objectives

Master

Understanding ASP.NET Core configuration system
Using the Options pattern for type-safe configuration
Configuring applications for different environments
Storing and accessing configuration securely

Develop

Understanding configuration management
Designing flexible configuration strategies
Appreciating configuration's role in deployment

Tips

Use the Options pattern for type-safe configuration access.
Store secrets in secure storage (Azure Key Vault, user secrets).
Use environment variables for deployment-specific values.
Validate configuration on application startup.

Common Pitfalls

Storing secrets in code or configuration files, creating security risks.
Not using strongly-typed options, losing type safety.
Not understanding configuration hierarchy, getting unexpected values.
Not validating configuration, causing runtime errors.

Summary

ASP.NET Core provides flexible configuration from multiple sources.
The Options pattern enables type-safe configuration access.
Configuration providers support various sources.
Understanding configuration enables flexible application deployment.
Configuration is essential for production applications.

Exercise

Create a strongly-typed configuration class and use it in your application.

// AppSettings.cs
public class AppSettings
{
    public string ApiKey { get; set; }
    public int MaxRetryAttempts { get; set; }
    public string DefaultConnection { get; set; }
}

// Program.cs
builder.Services.Configure<AppSettings>(builder.Configuration.GetSection("AppSettings"));

// Controller
public class ConfigController : Controller
{
    private readonly AppSettings _appSettings;
    
    public ConfigController(IOptions<AppSettings> appSettings)
    {
        _appSettings = appSettings.Value;
    }
    
    public IActionResult Index()
    {
        return Content($"API Key: {_appSettings.ApiKey}");
    }
}

Configuration and Options Pattern