This directory contains the modern IOptions<T> configuration classes for the SharePoint Sync Tool.

General application settings (name, version, environment, feature flags).

SharePoint Online connectivity settings with full validation:

• Username (required, email format)
• Password (required, use secrets management)
• SiteUrl (required, valid URL)
• Timeout and retry settings (range validated)

SQL Server connectivity and performance settings with validation:

• ConnectionString (required, use secrets management)
• CommandTimeout (range: 10-3600 seconds)
• BatchSize (range: 10-1000 items)
• EnforceEncryption flag

✅ Fail-Fast Validation - All configuration is validated at startup
✅ Strongly Typed - IntelliSense support and compile-time safety
✅ Testable - Easy to mock with Options.Create()
✅ Multiple Sources - JSON, environment variables, user secrets, command-line
✅ Secure - Supports secrets management out of the box

// Inject IOptions<T> in your service constructor
public class MyService
{
    private readonly SharePointOptions _options;
    
    public MyService(IOptions<SharePointOptions> options)
    {
        _options = options.Value; // Already validated!
    }
    
    public async Task DoWorkAsync()
    {
        // Use strongly-typed configuration
        var client = new Client(_options.SiteUrl);
        client.Timeout = TimeSpan.FromSeconds(_options.TimeoutSeconds);
    }
}

Configuration is loaded from multiple sources (priority order):

1. Command-line arguments (highest)
2. Environment variables (prefix: SPO2SQL_)
3. User secrets (development only)
4. appsettings.{Environment}.json
5. appsettings.json (lowest)

NEVER commit sensitive data to source control!

Use user secrets for sensitive data:

dotnet user-secrets set "SharePoint:Password" "your-password"
dotnet user-secrets set "Sql:ConnectionString" "Server=..."

Use environment variables:

export SPO2SQL_SharePoint__Password="your-password"
export SPO2SQL_Sql__ConnectionString="Server=..."

Note: Double underscore __ represents configuration hierarchy.

See MIGRATION_GUIDE.md for complete details on migrating from the legacy XML ConfigHelper pattern to IOptions<T>.

All configuration classes use Data Annotations for validation:

• [Required] - Value must be provided
• [EmailAddress] - Must be valid email format
• [Url] - Must be valid URL format
• [Range(min, max)] - Numeric values must be within range
• [MinLength(n)] - String must have minimum length

Validation happens at startup thanks to:

services.AddOptions<SharePointOptions>()
    .ValidateDataAnnotations()  // Enable attribute validation
    .ValidateOnStart();         // Validate immediately (fail-fast)

To add new configuration sections:

1. Create a new options class (e.g., MyServiceOptions.cs)
2. Add validation attributes
3. Register in Program.cs:

   services.AddOptions<MyServiceOptions>()
       .Bind(context.Configuration.GetSection("MyService"))
       .ValidateDataAnnotations()
       .ValidateOnStart();

4. Add section to appsettings.json
5. Inject IOptions<MyServiceOptions> where needed

Mock configuration in unit tests:

var mockOptions = Options.Create(new SharePointOptions
{
    SiteUrl = "https://test.sharepoint.com",
    Username = "test@test.com",
    Password = "test-password",
    TimeoutSeconds = 30
});

var service = new MyService(mockOptions);

• Application.cs - Demonstrates IOptions<T> patterns
• Program.cs - Configuration registration
• appsettings.json - Configuration values
• MIGRATION_GUIDE.md - XML to IOptions migration guide