Error Handling and Logging

55 min

ASP.NET Core provides built-in error handling mechanisms and logging capabilities, enabling you to handle errors gracefully and track application behavior. Error handling includes exception filters, middleware, and global error handlers. Logging provides structured output for debugging and monitoring. Understanding error handling and logging enables robust applications. Proper error handling and logging are essential for production.

You can use exception filters, middleware, and global error handling to catch and process exceptions at different levels. Exception filters catch exceptions in controllers/actions. Middleware catches exceptions in the pipeline. Global error handlers catch unhandled exceptions. Understanding different error handling approaches enables comprehensive error management. Different approaches suit different scenarios.

Structured logging with Serilog or other providers helps with debugging and monitoring by providing structured, searchable log output. Structured logging includes key-value pairs that enable filtering and analysis. Serilog, NLog, and other providers extend ASP.NET Core's built-in logging. Understanding structured logging enables effective debugging and monitoring. Structured logging is essential for production applications.

ASP.NET Core's built-in logging uses ILogger<T> and supports multiple log levels (Trace, Debug, Information, Warning, Error, Critical). Log levels control verbosity. Logging providers write to different outputs (console, file, database, etc.). Understanding logging levels and providers enables effective logging. Logging is built into ASP.NET Core.

Error pages can be customized for development (detailed errors) and production (user-friendly errors). Development error pages show stack traces and details. Production error pages hide sensitive information. Understanding error page configuration enables appropriate error display. Error pages should be user-friendly in production.

Best practices include logging at appropriate levels, using structured logging, not logging sensitive information, handling errors gracefully, and monitoring logs in production. Understanding error handling and logging enables robust applications. Error handling and logging are essential for production applications.

Key Concepts

ASP.NET Core provides built-in error handling and logging.
Exception filters, middleware, and global handlers catch errors.
Structured logging provides searchable, analyzable log output.
Logging supports multiple levels and providers.
Error pages differ for development and production.

Learning Objectives

Master

Implementing error handling with filters and middleware
Using ASP.NET Core's built-in logging
Implementing structured logging
Creating custom error pages

Develop

Understanding error handling strategies
Designing comprehensive logging systems
Appreciating error handling's role in reliability

Tips

Use structured logging for better searchability and analysis.
Log at appropriate levels—don't log everything as Information.
Handle errors gracefully—don't expose sensitive information.
Use different error pages for development and production.

Common Pitfalls

Not handling errors, causing application crashes.
Logging sensitive information (passwords, tokens), creating security risks.
Not using structured logging, making debugging difficult.
Showing detailed errors in production, exposing system information.

Summary

ASP.NET Core provides built-in error handling and logging.
Exception filters, middleware, and global handlers catch errors.
Structured logging enables effective debugging and monitoring.
Understanding error handling and logging enables robust applications.
Error handling and logging are essential for production.

Exercise

Implement global exception handling and custom error pages.

// Program.cs
if (app.Environment.IsDevelopment())
{
    app.UseDeveloperExceptionPage();
}
else
{
    app.UseExceptionHandler("/Error");
    app.UseHsts();
}

// ErrorController.cs
public class ErrorController : Controller
{
    [Route("Error")]
    public IActionResult Index()
    {
        return View("Error");
    }
    
    [Route("Error/{statusCode}")]
    public IActionResult HttpStatusCodeHandler(int statusCode)
    {
        ViewBag.ErrorMessage = $"Error {statusCode}";
        return View("Error");
    }
}

Error Handling and Logging