Learn how to implement robust exception handling in ASP.NET Core applications with detailed examples, best practices, and custom solutions.
Introduction
Exception handling is a critical aspect of building reliable and user-friendly applications. In ASP.NET Core, developers can leverage a variety of built-in tools and techniques to gracefully handle errors and provide meaningful feedback to users.
What is Exception Handling?
Exception handling refers to the process of capturing and managing errors during runtime. These errors, known as exceptions, can occur due to various reasons, such as invalid input, server issues, or external system failures. A robust exception-handling strategy ensures that such errors are properly handled without crashing the application.
Why Exception Handling Matters
Effective exception handling enhances the user experience, secures application data, and maintains application stability. Key benefits include:
- Preventing application crashes.
- Providing meaningful error messages to users.
- Improving debugging and logging.
- Enhancing application security by masking sensitive error details.
The following diagram illustrates Effective exception handling:
Built-in Error Handling in ASP.NET Core
ASP.NET Core offers several built-in features for error handling, such as:
DeveloperExceptionPageMiddleware: Displays detailed error pages in the development environment.UseExceptionHandler: Redirects to a custom error-handling endpoint.UseStatusCodePages: Displays responses for status codes like 404 or 500.
Using Exception Handling Middleware
Middleware is a core concept in ASP.NET Core for handling requests and responses. The UseExceptionHandler middleware is used for global exception handling:
// Configure exception handler in the middleware pipeline
app.UseExceptionHandler("/Error");
app.MapGet("/Error", (HttpContext context) =>
{
var feature = context.Features.Get<IExceptionHandlerFeature>();
return Results.Problem(detail: feature?.Error.Message, title: "An error occurred");
});
Custom Error Pages
Custom error pages improve user experience by providing user-friendly messages. Configure them using the UseStatusCodePages middleware:
// Adding status code pages for custom errors
app.UseStatusCodePagesWithReExecute("/Error/{0}");
Create a controller action to handle these errors:
[Route("Error/{statusCode}")]
public IActionResult Error(int statusCode)
{
switch (statusCode)
{
case 404:
return View("NotFound");
default:
return View("Error");
}
}
Exception Filters
Exception filters provide a way to handle exceptions at the controller or action level. Create a custom filter by implementing the IExceptionFilter interface:
public class CustomExceptionFilter : IExceptionFilter
{
public void OnException(ExceptionContext context)
{
context.Result = new ObjectResult(new
{
Message = "An error occurred while processing your request."
})
{
StatusCode = 500
};
}
}
Error Logging with Providers
ASP.NET Core integrates with logging providers like Serilog and NLog for comprehensive error logging. Add a logging provider in the Program.cs file:
builder.Logging.AddSerilog(new LoggerConfiguration()
.WriteTo.Console()
.WriteTo.File("logs/errors.txt")
.CreateLogger());
Handling Specific Exceptions
Use try-catch blocks to handle specific exceptions locally:
try
{
var result = await SomeOperationAsync();
}
catch (SqlException ex)
{
logger.LogError("Database error occurred: {Message}", ex.Message);
}
catch (Exception ex)
{
logger.LogError("Unexpected error occurred: {Message}", ex.Message);
}
Best Practices for Exception Handling
- Always log exceptions for debugging and monitoring.
- Hide sensitive information in error responses.
- Use global error handling for consistency.
- Test error handling thoroughly.
- Leverage third-party tools for advanced logging and monitoring.
Conclusion
Exception handling is an integral part of application development. By implementing robust error-handling strategies in ASP.NET Core, you can create reliable, user-friendly, and secure applications. Understanding and leveraging tools like middleware, filters, and logging providers will help you handle errors effectively and maintain application stability.