ILogger Interface

What is Logging?

Logging records events that happen in your application. It helps with debugging, monitoring, and understanding application behavior.

ILogger Interface

ASP.NET Core provides the ILogger<T> interface for logging.

Dependency Injection

public class ProductsController : Controller
{
    private readonly ILogger<ProductsController> _logger;

    public ProductsController(ILogger<ProductsController> logger)
    {
        _logger = logger;
    }
}

Basic Logging Methods

_logger.LogTrace("Trace message");
_logger.LogDebug("Debug message");
_logger.LogInformation("Information message");
_logger.LogWarning("Warning message");
_logger.LogError("Error message");
_logger.LogCritical("Critical message");

Logging with Parameters

_logger.LogInformation("Product {ProductId} created by {UserId}", productId, userId);

Logging Exceptions

try
{
    // Some operation
}
catch (Exception ex)
{
    _logger.LogError(ex, "Failed to create product {ProductId}", productId);
}

InvenTrack Example

public class ProductsController : Controller
{
    private readonly ILogger<ProductsController> _logger;
    private readonly InvenTrackDbContext _context;

    [HttpPost]
    public async Task<IActionResult> Create(Product product)
    {
        _logger.LogInformation("Creating product {ProductName}", product.Name);

        try
        {
            _context.Products.Add(product);
            await _context.SaveChangesAsync();

            _logger.LogInformation("Product {ProductId} created successfully", product.Id);
            return RedirectToAction("Index");
        }
        catch (Exception ex)
        {
            _logger.LogError(ex, "Failed to create product {ProductName}", product.Name);
            return View(product);
        }
    }
}

Key Takeaways

• ILogger<T>: Logging interface
• Dependency injection: Inject ILogger in constructor
• Log methods: LogTrace, LogDebug, LogInformation, LogWarning, LogError, LogCritical
• Parameters: Use placeholders {Name} for structured logging
• Exceptions: Pass exception as first parameter