What are the different ways to manage application configuration?

ASP.NET Core provides multiple ways to manage configuration:

1. appsettings.json (Most Common)

{
  "Logging": {
    "LogLevel": {
      "Default": "Information"
    }
  },
  "ConnectionStrings": {
    "DefaultConnection": "Server=.;Database=MyDb;Trusted_Connection=true;"
  },
  "AppSettings": {
    "ApplicationName": "MyApp",
    "MaxFileSize": 10485760
  }
}

2. Environment-Specific Configuration

appsettings.json (base configuration)
appsettings.Development.json (development overrides)
appsettings.Production.json (production overrides)

3. User Secrets (Development Only)

dotnet user-secrets init
dotnet user-secrets set "ApiKey" "secret-key-value"

4. Environment Variables

// Access in code
var apiKey = builder.Configuration["ApiKey"];

// Set in launchSettings.json
"environmentVariables": {
    "ASPNETCORE_ENVIRONMENT": "Development",
    "ApiKey": "dev-key"
}

5. Command Line Arguments

dotnet run --ApiKey="command-line-key"

6. Azure Key Vault

builder.Configuration.AddAzureKeyVault(
    new Uri("https://myvault.vault.azure.net/"),
    new DefaultAzureCredential());

7. Options Pattern (Strongly Typed)

// Settings class
public class AppSettings
{
    public string ApplicationName { get; set; }
    public int MaxFileSize { get; set; }
}

// Register
builder.Services.Configure(
    builder.Configuration.GetSection("AppSettings"));

// Use in controller
public class HomeController : Controller
{
    private readonly AppSettings _settings;

    public HomeController(IOptions settings)
    {
        _settings = settings.Value;
    }
}

Configuration Priority (Highest to Lowest):

1. Command-line arguments
2. Environment variables
3. User secrets
4. appsettings.{Environment}.json
5. appsettings.json