MSDN Documentation

Understanding Error Types

Errors can manifest in various forms, each requiring a distinct approach:

• System Errors: Occur due to issues with the underlying operating system or hardware.
• Application Errors: Bugs or unexpected conditions within your code.
• User Input Errors: Invalid data provided by the user.
• Network Errors: Problems communicating with external services or databases.

Exception Handling Best Practices

Leveraging exceptions is a powerful way to manage errors gracefully. Follow these guidelines:

• Use Exceptions for Exceptional Conditions: Don't use exceptions for normal control flow.
• Catch Specific Exceptions: Avoid catching the base Exception class unless absolutely necessary. This allows for more targeted error recovery.
• Never Swallow Exceptions: Always handle or rethrow exceptions. Logging them is a minimum requirement.
• Provide Contextual Information: Include details in your exception messages that aid in debugging.
• Clean Up Resources: Use try-finally blocks or the using statement to ensure resources are released, even if an exception occurs.

Example: Using try-catch-finally

try
{
    // Code that might throw an exception
    FileStream fs = new FileStream("data.txt", FileMode.Open);
    // ... process the file ...
    fs.Close(); // Ensure file is closed if no exception
}
catch (FileNotFoundException ex)
{
    Console.WriteLine("Error: The specified file was not found.");
    // Log the exception: LogError(ex);
}
catch (IOException ex)
{
    Console.WriteLine("An I/O error occurred.");
    // Log the exception: LogError(ex);
}
finally
{
    // This block always executes, regardless of whether an exception occurred
    // Dispose of any resources that might not have been closed in the try block
    if (fs != null && fs.CanRead) // Example check
    {
        fs.Dispose();
    }
    Console.WriteLine("Cleanup complete.");
}
                    

Custom Exception Classes

For application-specific errors, consider creating custom exception classes. This improves code readability and allows for more granular error handling.

public class InvalidUserDataException : Exception
{
    public string InvalidField { get; private set; }

    public InvalidUserDataException(string message, string invalidField)
        : base(message)
    {
        InvalidField = invalidField;
    }

    public InvalidUserDataException(string message, Exception innerException, string invalidField)
        : base(message, innerException)
    {
        InvalidField = invalidField;
    }
}
                    

Usage:

if (string.IsNullOrEmpty(userName))
{
    throw new InvalidUserDataException("Username cannot be empty.", "UserName");
}
                    

Error Logging and Monitoring

A robust error logging mechanism is essential for diagnosing and resolving issues in production environments. Integrate with logging frameworks like Serilog, NLog, or the built-in diagnostics capabilities.

Consider using Application Performance Monitoring (APM) tools to track errors, exceptions, and performance bottlenecks in real-time.

Handling External Service Errors

When interacting with external APIs or services, anticipate potential failures:

• Implement retry mechanisms with exponential backoff for transient errors.
• Handle specific HTTP status codes (e.g., 4xx for client errors, 5xx for server errors).
• Consider circuit breaker patterns to prevent cascading failures.

public async Task<string> GetDataFromExternalServiceAsync(string url)
{
    int maxRetries = 3;
    TimeSpan delay = TimeSpan.FromSeconds(1);

    for (int i = 0; i < maxRetries; i++)
    {
        try
        {
            using (var client = new HttpClient())
            {
                var response = await client.GetAsync(url);
                response.EnsureSuccessStatusCode(); // Throws exception for non-success status codes
                return await response.Content.ReadAsStringAsync();
            }
        }
        catch (HttpRequestException ex)
        {
            // Log the retry attempt
            Console.WriteLine($"Attempt {i + 1} failed: {ex.Message}");
            await Task.Delay(delay);
            delay *= 2; // Exponential backoff
        }
    }
    throw new InvalidOperationException($"Failed to retrieve data from {url} after {maxRetries} retries.");
}
                    

User Interface Error Feedback

Provide clear and actionable feedback to users when errors occur. Avoid technical jargon. Highlight the problematic input or explain what went wrong in simple terms.