Windows Error Handling - C# Samples

using System;
using System.IO;
using System.Collections.Generic;
using System.Threading.Tasks;

class ExceptionHandlingExamples
{
    // 1. Basic try-catch example
    public static void BasicTryCatch()
    {
        Console.WriteLine("=== Basic Try-Catch Example ===");

        try
        {
            // This will throw a DivideByZeroException
            int result = 10 / 0;
            Console.WriteLine($"Result: {result}");
        }
        catch (DivideByZeroException ex)
        {
            Console.WriteLine($"Caught DivideByZeroException: {ex.Message}");
        }
        catch (Exception ex)
        {
            Console.WriteLine($"Caught general exception: {ex.Message}");
        }
        finally
        {
            Console.WriteLine("Finally block always executes");
        }
    }

    // 2. Multiple catch blocks
    public static void MultipleCatchBlocks()
    {
        Console.WriteLine("
=== Multiple Catch Blocks Example ===");

        string[] testCases = { "123", "abc", null, "" };

        foreach (string testCase in testCases)
        {
            try
            {
                Console.WriteLine($"
Processing: {testCase ?? "null"}");
                int number = int.Parse(testCase);
                int result = 100 / number;
                Console.WriteLine($"Success! Result: {result}");
            }
            catch (FormatException ex)
            {
                Console.WriteLine($"Format Exception: {ex.Message}");
            }
            catch (ArgumentNullException ex)
            {
                Console.WriteLine($"Argument Null Exception: {ex.Message}");
            }
            catch (DivideByZeroException ex)
            {
                Console.WriteLine($"Divide By Zero Exception: {ex.Message}");
            }
            catch (Exception ex)
            {
                Console.WriteLine($"Unexpected Exception: {ex.Message}");
            }
        }
    }

    // 3. Nested try-catch
    public static void NestedTryCatch()
    {
        Console.WriteLine("
=== Nested Try-Catch Example ===");

        try
        {
            Console.WriteLine("Outer try block started");

            try
            {
                Console.WriteLine("Inner try block started");
                // Attempt to read a non-existent file
                string content = File.ReadAllText("nonexistent.txt");
                Console.WriteLine("File read successfully");
            }
            catch (FileNotFoundException ex)
            {
                Console.WriteLine($"Inner catch - File not found: {ex.Message}");
                throw new InvalidOperationException("File processing failed", ex);
            }

            Console.WriteLine("Outer try block continued");
        }
        catch (InvalidOperationException ex)
        {
            Console.WriteLine($"Outer catch - Invalid operation: {ex.Message}");
            if (ex.InnerException != null)
            {
                Console.WriteLine($"Inner exception: {ex.InnerException.Message}");
            }
        }
    }

    // 4. Custom exception class
    public class InvalidAgeException : Exception
    {
        public InvalidAgeException() : base("Age must be between 0 and 150") { }
        public InvalidAgeException(string message) : base(message) { }
        public InvalidAgeException(string message, Exception inner) : base(message, inner) { }
    }

    public static void CustomExceptions()
    {
        Console.WriteLine("
=== Custom Exceptions Example ===");

        List<int> ages = { 25, -5, 200, 30 };

        foreach (int age in ages)
        {
            try
            {
                ValidateAge(age);
                Console.WriteLine($"Age {age} is valid");
            }
            catch (InvalidAgeException ex)
            {
                Console.WriteLine($"Invalid age {age}: {ex.Message}");
            }
        }
    }

    private static void ValidateAge(int age)
    {
        if (age < 0 || age > 150)
        {
            throw new InvalidAgeException($"Age {age} is not valid. Must be between 0 and 150.");
        }
    }

    // 5. Exception filters (C# 6.0+)
    public static void ExceptionFilters()
    {
        Console.WriteLine("
=== Exception Filters Example ===");

        string[] urls = {
            "https://valid.example.com",
            "invalid-url",
            "http://timeout.example.com"
        };

        foreach (string url in urls)
        {
            try
            {
                // Simulate HTTP request
                if (url.StartsWith("https://valid"))
                {
                    Console.WriteLine($"Successfully connected to {url}");
                }
                else if (url == "invalid-url")
                {
                    throw new UriFormatException("Invalid URI format");
                }
                else
                {
                    throw new TimeoutException("Connection timeout");
                }
            }
            catch (Exception ex) when (ex is UriFormatException)
            {
                Console.WriteLine($"URI Error for {url}: {ex.Message}");
            }
            catch (Exception ex) when (ex is TimeoutException)
            {
                Console.WriteLine($"Timeout Error for {url}: {ex.Message}");
            }
            catch (Exception ex)
            {
                Console.WriteLine($"General Error for {url}: {ex.Message}");
            }
        }
    }

    // 6. Using statement for resource management
    public static void UsingStatement()
    {
        Console.WriteLine("
=== Using Statement Example ===");

        try
        {
            // Create a test file
            File.WriteAllText("test.txt", "Hello, World!");

            // Using statement ensures proper disposal
            using (StreamReader reader = new StreamReader("test.txt"))
            {
                string content = reader.ReadToEnd();
                Console.WriteLine($"File content: {content}");
            } // reader is automatically disposed here

            // Try to use the disposed reader (this would fail if we tried)
            Console.WriteLine("File reader properly disposed");
        }
        catch (Exception ex)
        {
            Console.WriteLine($"Error: {ex.Message}");
        }
        finally
        {
            // Cleanup
            if (File.Exists("test.txt"))
            {
                File.Delete("test.txt");
                Console.WriteLine("Test file cleaned up");
            }
        }
    }

    // 7. Async exception handling
    public static async Task AsyncExceptionHandling()
    {
        Console.WriteLine("
=== Async Exception Handling Example ===");

        List<string> urls = {
            "https://valid.example.com",
            "invalid-url",
            "https://timeout.example.com"
        };

        foreach (string url in urls)
        {
            try
            {
                string result = await SimulateHttpRequestAsync(url);
                Console.WriteLine($"Success: {result}");
            }
            catch (HttpRequestException ex)
            {
                Console.WriteLine($"HTTP Error for {url}: {ex.Message}");
            }
            catch (TaskCanceledException ex)
            {
                Console.WriteLine($"Timeout for {url}: {ex.Message}");
            }
            catch (Exception ex)
            {
                Console.WriteLine($"Unexpected error for {url}: {ex.Message}");
            }
        }
    }

    private static async Task<string> SimulateHttpRequestAsync(string url)
    {
        await Task.Delay(100); // Simulate network delay

        if (url == "invalid-url")
        {
            throw new HttpRequestException("Invalid URL format");
        }

        if (url.Contains("timeout"))
        {
            throw new TaskCanceledException("Request timed out");
        }

        return $"Response from {url}";
    }

    // 8. Aggregate exception handling
    public static void AggregateExceptionHandling()
    {
        Console.WriteLine("
=== Aggregate Exception Example ===");

        List<Task> tasks = new List<Task>();

        // Create multiple tasks that might fail
        tasks.Add(Task.Run(() => {
            throw new InvalidOperationException("Task 1 failed");
        }));

        tasks.Add(Task.Run(() => {
            throw new ArgumentException("Task 2 failed");
        }));

        tasks.Add(Task.Run(() => {
            Console.WriteLine("Task 3 completed successfully");
        }));

        try
        {
            Task.WaitAll(tasks.ToArray());
            Console.WriteLine("All tasks completed successfully");
        }
        catch (AggregateException ex)
        {
            Console.WriteLine($"AggregateException caught with {ex.InnerExceptions.Count} inner exceptions:");

            foreach (Exception innerEx in ex.InnerExceptions)
            {
                Console.WriteLine($"  - {innerEx.GetType().Name}: {innerEx.Message}");
            }

            // Handle individual exceptions
            ex.Handle(innerEx =>
            {
                if (innerEx is InvalidOperationException)
                {
                    Console.WriteLine($"Handled InvalidOperationException: {innerEx.Message}");
                    return true; // Exception handled
                }
                else if (innerEx is ArgumentException)
                {
                    Console.WriteLine($"Handled ArgumentException: {innerEx.Message}");
                    return true; // Exception handled
                }
                return false; // Exception not handled
            });
        }
    }

    static void Main(string[] args)
    {
        Console.WriteLine("=== C# Exception Handling Examples ===
");

        try
        {
            BasicTryCatch();
            MultipleCatchBlocks();
            NestedTryCatch();
            CustomExceptions();
            ExceptionFilters();
            UsingStatement();

            Console.WriteLine("
=== Async Examples ===");
            AsyncExceptionHandling().GetAwaiter().GetResult();

            Console.WriteLine("
=== Parallel Processing Examples ===");
            AggregateExceptionHandling();

            Console.WriteLine("
All exception handling examples completed successfully!");
        }
        catch (Exception ex)
        {
            Console.WriteLine($"Unexpected error in main program: {ex.Message}");
        }
    }
}

using System;
using System.IO;
using System.Collections.Generic;
using System.Threading;

// Enum for log levels
public enum LogLevel
{
    Debug = 0,
    Info = 1,
    Warning = 2,
    Error = 3,
    Critical = 4
}

// Custom logger class
public class Logger
{
    private readonly string _logFilePath;
    private readonly LogLevel _minLogLevel;
    private readonly object _lockObject = new object();

    public Logger(string logFilePath, LogLevel minLogLevel = LogLevel.Info)
    {
        _logFilePath = logFilePath;
        _minLogLevel = minLogLevel;

        // Ensure log directory exists
        string logDirectory = Path.GetDirectoryName(logFilePath);
        if (!string.IsNullOrEmpty(logDirectory) && !Directory.Exists(logDirectory))
        {
            Directory.CreateDirectory(logDirectory);
        }

        // Write initial log entry
        LogInfo($"Logger initialized. Log file: {_logFilePath}, Min level: {_minLogLevel}");
    }

    // Core logging method
    private void WriteLog(LogLevel level, string message, Exception exception = null)
    {
        if (level < _minLogLevel)
            return;

        lock (_lockObject)
        {
            string timestamp = DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss");
            string levelStr = level.ToString().ToUpper().PadRight(8);
            string threadId = Thread.CurrentThread.ManagedThreadId.ToString();

            string logEntry = $"[{timestamp}] [{levelStr}] [T:{threadId}] {message}";

            if (exception != null)
            {
                logEntry += $"\nException: {exception.GetType().Name}: {exception.Message}";
                logEntry += $"\nStackTrace: {exception.StackTrace}";
            }

            // Write to console
            Console.WriteLine(logEntry);

            // Write to file
            try
            {
                File.AppendAllText(_logFilePath, logEntry + Environment.NewLine);
            }
            catch (Exception ex)
            {
                Console.WriteLine($"Failed to write to log file: {ex.Message}");
            }
        }
    }

    // Convenience methods for different log levels
    public void LogDebug(string message)
    {
        WriteLog(LogLevel.Debug, message);
    }

    public void LogInfo(string message)
    {
        WriteLog(LogLevel.Info, message);
    }

    public void LogWarning(string message)
    {
        WriteLog(LogLevel.Warning, message);
    }

    public void LogError(string message, Exception exception = null)
    {
        WriteLog(LogLevel.Error, message, exception);
    }

    public void LogCritical(string message, Exception exception = null)
    {
        WriteLog(LogLevel.Critical, message, exception);
    }
}

// Logger factory for managing multiple loggers
public static class LoggerFactory
{
    private static readonly Dictionary<string, Logger> _loggers = new Dictionary<string, Logger>();
    private static readonly object _lockObject = new object();

    public static Logger GetLogger(string name, LogLevel minLogLevel = LogLevel.Info)
    {
        lock (_lockObject)
        {
            if (!_loggers.ContainsKey(name))
            {
                string logPath = $"logs/{name}_{DateTime.Now:yyyyMMdd}.log";
                _loggers[name] = new Logger(logPath, minLogLevel);
            }
            return _loggers[name];
        }
    }

    public static void CloseAllLoggers()
    {
        lock (_lockObject)
        {
            foreach (var logger in _loggers.Values)
            {
                logger.LogInfo("Logger shutting down");
            }
            _loggers.Clear();
        }
    }
}

// Example usage class
public class LoggingExamples
{
    private readonly Logger _logger;

    public LoggingExamples()
    {
        _logger = LoggerFactory.GetLogger("LoggingExamples");
    }

    // 1. Basic logging examples
    public void BasicLogging()
    {
        _logger.LogInfo("Starting basic logging examples");

        _logger.LogDebug("This is a debug message - only visible in debug mode");
        _logger.LogInfo("This is an info message - normal operation information");
        _logger.LogWarning("This is a warning - potential issue detected");

        try
        {
            // Simulate an error
            throw new InvalidOperationException("This is a simulated error");
        }
        catch (Exception ex)
        {
            _logger.LogError("An error occurred during processing", ex);
        }

        _logger.LogCritical("This is a critical message - system may be unstable");
    }

    // 2. Logging in different methods
    public void MethodWithLogging(string parameter)
    {
        _logger.LogDebug($"Entering MethodWithLogging with parameter: {parameter}");

        try
        {
            if (string.IsNullOrEmpty(parameter))
            {
                _logger.LogWarning("Empty parameter provided");
                return;
            }

            if (parameter.Length < 3)
            {
                throw new ArgumentException("Parameter must be at least 3 characters long");
            }

            _logger.LogInfo($"Successfully processed parameter: {parameter}");

            // Simulate some work
            Thread.Sleep(100);

        }
        catch (Exception ex)
        {
            _logger.LogError($"Failed to process parameter: {parameter}", ex);
            throw;
        }
        finally
        {
            _logger.LogDebug("Exiting MethodWithLogging");
        }
    }

    // 3. Performance logging
    public void PerformanceLogging()
    {
        _logger.LogInfo("Starting performance measurement");

        var startTime = DateTime.Now;

        try
        {
            // Simulate some work
            for (int i = 0; i < 1000; i++)
            {
                double result = Math.Sqrt(i);
                if (i % 100 == 0)
                {
                    _logger.LogDebug($"Processed {i} items, current result: {result:F2}");
                }
            }

            var duration = DateTime.Now - startTime;
            _logger.LogInfo($"Performance test completed in {duration.TotalMilliseconds:F2}ms");
        }
        catch (Exception ex)
        {
            _logger.LogError("Performance test failed", ex);
        }
    }

    // 4. Logging from multiple threads
    public void MultiThreadedLogging()
    {
        _logger.LogInfo("Starting multi-threaded logging test");

        List<Thread> threads = new List<Thread>();

        for (int i = 0; i < 5; i++)
        {
            int threadId = i;
            Thread thread = new Thread(() =>
            {
                for (int j = 0; j < 10; j++)
                {
                    _logger.LogInfo($"Thread {threadId} - Message {j}");
                    Thread.Sleep(50);
                }
            });

            threads.Add(thread);
            thread.Start();
        }

        // Wait for all threads to complete
        foreach (var thread in threads)
        {
            thread.Join();
        }

        _logger.LogInfo("Multi-threaded logging test completed");
    }

    // 5. Structured logging
    public void StructuredLogging()
    {
        _logger.LogInfo("Starting structured logging examples");

        // Log user action
        string userId = "user123";
        string action = "login";
        string ip = "192.168.1.100";

        _logger.LogInfo($"User action - ID: {userId}, Action: {action}, IP: {ip}");

        // Log business event
        string orderId = "ORD-001";
        decimal amount = 99.99m;
        string status = "completed";

        _logger.LogInfo($"Order processed - ID: {orderId}, Amount: {amount:C}, Status: {status}");

        // Log system metrics
        double cpuUsage = 75.5;
        long memoryUsage = 1024 * 1024 * 512; // 512 MB
        int activeConnections = 42;

        _logger.LogInfo($"System metrics - CPU: {cpuUsage:F1}%, Memory: {memoryUsage / 1024 / 1024}MB, Connections: {activeConnections}");
    }
}

class Program1
{
    static void Main(string[] args)
    {
        Console.WriteLine("=== C# Logging Examples ===\n");

        try
        {
            // Create examples instance
            var examples = new LoggingExamples();

            // Run different logging examples
            examples.BasicLogging();
            Console.WriteLine();

            examples.MethodWithLogging("Hello");
            examples.MethodWithLogging("Hi");
            examples.MethodWithLogging(""); // This will log a warning
            Console.WriteLine();

            try
            {
                examples.MethodWithLogging("AB"); // This will throw an exception
            }
            catch
            {
                Console.WriteLine("Expected exception caught");
            }
            Console.WriteLine();

            examples.PerformanceLogging();
            Console.WriteLine();

            examples.MultiThreadedLogging();
            Console.WriteLine();

            examples.StructuredLogging();

            Console.WriteLine("\nAll logging examples completed!");
            Console.WriteLine($"Check the 'logs' directory for log files.");
        }
        catch (Exception ex)
        {
            Console.WriteLine($"Unexpected error: {ex.Message}");
        }
        finally
        {
            // Clean up
            LoggerFactory.CloseAllLoggers();
        }
    }
}

using System;
using System.Collections.Generic;
using System.Text.RegularExpressions;

// Custom validation exception
public class ValidationException : Exception
{
    public ValidationException(string message) : base(message) { }
    public ValidationException(string message, Exception inner) : base(message, inner) { }
}

// Validation helper class
public static class Validator
{
    // 1. Null and empty checks
    public static void NotNull(object value, string parameterName)
    {
        if (value == null)
        {
            throw new ArgumentNullException(parameterName, $"Parameter '{parameterName}' cannot be null");
        }
    }

    public static void NotNullOrEmpty(string value, string parameterName)
    {
        NotNull(value, parameterName);
        if (string.IsNullOrEmpty(value))
        {
            throw new ArgumentException($"Parameter '{parameterName}' cannot be null or empty", parameterName);
        }
    }

    public static void NotNullOrWhiteSpace(string value, string parameterName)
    {
        NotNull(value, parameterName);
        if (string.IsNullOrWhiteSpace(value))
        {
            throw new ArgumentException($"Parameter '{parameterName}' cannot be null, empty, or whitespace", parameterName);
        }
    }

    // 2. Range validation
    public static void InRange(int value, int min, int max, string parameterName)
    {
        if (value < min || value > max)
        {
            throw new ArgumentOutOfRangeException(parameterName, value, $"Parameter '{parameterName}' must be between {min} and {max}");
        }
    }

    public static void InRange(double value, double min, double max, string parameterName)
    {
        if (value < min || value > max)
        {
            throw new ArgumentOutOfRangeException(parameterName, value, $"Parameter '{parameterName}' must be between {min} and {max}");
        }
    }

    public static void Positive(int value, string parameterName)
    {
        if (value <= 0)
        {
            throw new ArgumentOutOfRangeException(parameterName, value, $"Parameter '{parameterName}' must be positive");
        }
    }

    public static void NonNegative(int value, string parameterName)
    {
        if (value < 0)
        {
            throw new ArgumentOutOfRangeException(parameterName, value, $"Parameter '{parameterName}' must be non-negative");
        }
    }

    // 3. String validation
    public static void Length(string value, int minLength, int maxLength, string parameterName)
    {
        NotNull(value, parameterName);
        if (value.Length < minLength || value.Length > maxLength)
        {
            throw new ArgumentException($"Parameter '{parameterName}' length must be between {minLength} and {maxLength} characters", parameterName);
        }
    }

    public static void Matches(string value, string pattern, string parameterName)
    {
        NotNull(value, parameterName);
        NotNull(pattern, nameof(pattern));

        if (!Regex.IsMatch(value, pattern))
        {
            throw new ArgumentException($"Parameter '{parameterName}' does not match the required pattern: {pattern}", parameterName);
        }
    }

    public static void Email(string value, string parameterName)
    {
        NotNull(value, parameterName);
        string emailPattern = @"^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$";
        Matches(value, emailPattern, parameterName);
    }

    public static void PhoneNumber(string value, string parameterName)
    {
        NotNull(value, parameterName);
        string phonePattern = @"^\+?[1-9]\d{1,14}$";
        if (!Regex.IsMatch(value, phonePattern))
        {
            throw new ArgumentException($"Parameter '{parameterName}' is not a valid phone number", parameterName);
        }
    }

    // 4. Collection validation
    public static void NotEmpty<T>(IEnumerable<T> collection, string parameterName)
    {
        NotNull(collection, parameterName);
        if (!collection.GetEnumerator().MoveNext())
        {
            throw new ArgumentException($"Parameter '{parameterName}' cannot be empty", parameterName);
        }
    }

    public static void Count<T>(IEnumerable<T> collection, int minCount, int maxCount, string parameterName)
    {
        NotNull(collection, parameterName);

        int count = 0;
        foreach (var item in collection)
        {
            count++;
        }

        if (count < minCount || count > maxCount)
        {
            throw new ArgumentException($"Parameter '{parameterName}' must contain between {minCount} and {maxCount} items", parameterName);
        }
    }

    // 5. Date validation
    public static void InFuture(DateTime value, string parameterName)
    {
        if (value <= DateTime.Now)
        {
            throw new ArgumentOutOfRangeException(parameterName, value, $"Parameter '{parameterName}' must be in the future");
        }
    }

    public static void InPast(DateTime value, string parameterName)
    {
        if (value >= DateTime.Now)
        {
            throw new ArgumentOutOfRangeException(parameterName, value, $"Parameter '{parameterName}' must be in the past");
        }
    }

    public static void Between(DateTime value, DateTime min, DateTime max, string parameterName)
    {
        if (value < min || value > max)
        {
            throw new ArgumentOutOfRangeException(parameterName, value, $"Parameter '{parameterName}' must be between {min:yyyy-MM-dd} and {max:yyyy-MM-dd}");
        }
    }

    // 6. Custom validation
    public static void Custom<T>(T value, Func<T, bool> validationFunc, string errorMessage, string parameterName)
    {
        NotNull(validationFunc, nameof(validationFunc));
        NotNull(value, parameterName);

        if (!validationFunc(value))
        {
            throw new ValidationException($"Parameter '{parameterName}' validation failed: {errorMessage}");
        }
    }
}

// User class with validation
public class User
{
    public string Id { get; }
    public string Name { get; }
    public string Email { get; }
    public int Age { get; }
    public DateTime BirthDate { get; }
    public string PhoneNumber { get; }

    public User(string name, string email, int age, DateTime birthDate, string phoneNumber)
    {
        // Validate all parameters
        Validator.NotNullOrWhiteSpace(name, nameof(name));
        Validator.Length(name, 2, 50, nameof(name));

        Validator.Email(email, nameof(email));

        Validator.InRange(age, 0, 150, nameof(age));

        Validator.InPast(birthDate, nameof(birthDate));

        Validator.PhoneNumber(phoneNumber, nameof(phoneNumber));

        // Additional custom validation
        Validator.Custom(age, a => CalculateAge(birthDate) == a, "Age does not match birth date", nameof(age));

        // Assign properties
        Id = Guid.NewGuid().ToString();
        Name = name.Trim();
        Email = email.ToLowerInvariant();
        Age = age;
        BirthDate = birthDate;
        PhoneNumber = phoneNumber;
    }

    private static int CalculateAge(DateTime birthDate)
    {
        int age = DateTime.Now.Year - birthDate.Year;
        if (birthDate > DateTime.Now.AddYears(-age))
        {
            age--;
        }
        return age;
    }

    public override string ToString()
    {
        return $"User: {Name}, Email: {Email}, Age: {Age}, Phone: {PhoneNumber}";
    }
}

// Order class with validation
public class Order
{
    public string OrderId { get; }
    public List<OrderItem> Items { get; }
    public DateTime OrderDate { get; }
    public decimal TotalAmount { get; }
    public string CustomerEmail { get; }

    public Order(List<OrderItem> items, string customerEmail)
    {
        Validator.NotEmpty(items, nameof(items));
        Validator.Count(items, 1, 100, nameof(items));
        Validator.Email(customerEmail, nameof(customerEmail));

        // Validate each item
        foreach (var item in items)
        {
            Validator.Positive(item.Quantity, nameof(item.Quantity));
            Validator.Positive(item.Price, nameof(item.Price));
        }

        OrderId = "ORD-" + Guid.NewGuid().ToString("N")[..8].ToUpper();
        Items = new List<OrderItem>(items);
        OrderDate = DateTime.Now;
        TotalAmount = CalculateTotal();
        CustomerEmail = customerEmail.ToLowerInvariant();
    }

    private decimal CalculateTotal()
    {
        decimal total = 0;
        foreach (var item in Items)
        {
            total += item.Quantity * item.Price;
        }
        return total;
    }

    public override string ToString()
    {
        return $"Order {OrderId}: {Items.Count} items, Total: {TotalAmount:C}";
    }
}

public class OrderItem
{
    public string ProductName { get; }
    public int Quantity { get; }
    public decimal Price { get; }

    public OrderItem(string productName, int quantity, decimal price)
    {
        Validator.NotNullOrWhiteSpace(productName, nameof(productName));
        Validator.Length(productName, 1, 100, nameof(productName));
        Validator.Positive(quantity, nameof(quantity));
        Validator.Positive(price, nameof(price));

        ProductName = productName;
        Quantity = quantity;
        Price = price;
    }
}

// Validation examples class
public class ValidationExamples
{
    // 1. Basic parameter validation
    public static void BasicValidation()
    {
        Console.WriteLine("=== Basic Parameter Validation ===");

        // Valid cases
        try
        {
            Validator.NotNull("hello", "test");
            Console.WriteLine("✓ NotNull validation passed");

            Validator.InRange(25, 0, 100, "age");
            Console.WriteLine("✓ Range validation passed");

            Validator.Positive(10, "count");
            Console.WriteLine("✓ Positive validation passed");
        }
        catch (Exception ex)
        {
            Console.WriteLine($"Unexpected error: {ex.Message}");
        }

        // Invalid cases
        try
        {
            Validator.NotNull(null, "test");
        }
        catch (ArgumentNullException ex)
        {
            Console.WriteLine($"✓ NotNull validation failed as expected: {ex.Message}");
        }

        try
        {
            Validator.InRange(150, 0, 100, "age");
        }
        catch (ArgumentOutOfRangeException ex)
        {
            Console.WriteLine($"✓ Range validation failed as expected: {ex.Message}");
        }
    }

    // 2. String validation
    public static void StringValidation()
    {
        Console.WriteLine("\n=== String Validation ===");

        // Valid cases
        try
        {
            Validator.NotNullOrEmpty("Hello World", "message");
            Console.WriteLine("✓ NotNullOrEmpty validation passed");

            Validator.Length("Test", 2, 10, "text");
            Console.WriteLine("✓ Length validation passed");

            Validator.Email("user@example.com", "email");
            Console.WriteLine("✓ Email validation passed");

            Validator.Matches("ABC123", @"^[A-Z]{3}[0-9]{3}$", "code");
            Console.WriteLine("✓ Pattern validation passed");
        }
        catch (Exception ex)
        {
            Console.WriteLine($"Unexpected error: {ex.Message}");
        }

        // Invalid cases
        try
        {
            Validator.Email("invalid-email", "email");
        }
        catch (ArgumentException ex)
        {
            Console.WriteLine($"✓ Email validation failed as expected: {ex.Message}");
        }
    }

    // 3. Collection validation
    public static void CollectionValidation()
    {
        Console.WriteLine("\n=== Collection Validation ===");

        // Valid cases
        var validList = new List<string> { "item1", "item2", "item3" };
        try
        {
            Validator.NotEmpty(validList, "items");
            Console.WriteLine("✓ NotEmpty validation passed");

            Validator.Count(validList, 1, 10, "items");
            Console.WriteLine("✓ Count validation passed");
        }
        catch (Exception ex)
        {
            Console.WriteLine($"Unexpected error: {ex.Message}");
        }

        // Invalid cases
        try
        {
            Validator.NotEmpty(new List<string>(), "items");
        }
        catch (ArgumentException ex)
        {
            Console.WriteLine($"✓ NotEmpty validation failed as expected: {ex.Message}");
        }
    }

    // 4. Date validation
    public static void DateValidation()
    {
        Console.WriteLine("\n=== Date Validation ===");

        // Valid cases
        try
        {
            Validator.InPast(DateTime.Now.AddDays(-1), "pastDate");
            Console.WriteLine("✓ Past date validation passed");

            Validator.InFuture(DateTime.Now.AddDays(1), "futureDate");
            Console.WriteLine("✓ Future date validation passed");
        }
        catch (Exception ex)
        {
            Console.WriteLine($"Unexpected error: {ex.Message}");
        }

        // Invalid cases
        try
        {
            Validator.InFuture(DateTime.Now.AddDays(-1), "futureDate");
        }
        catch (ArgumentOutOfRangeException ex)
        {
            Console.WriteLine($"✓ Future date validation failed as expected: {ex.Message}");
        }
    }

    // 5. Custom validation
    public static void CustomValidation()
    {
        Console.WriteLine("\n=== Custom Validation ===");

        // Valid case
        try
        {
            Validator.Custom("12345", value => value.Length == 5 && value.All(char.IsDigit), "Must be 5 digits", "zipCode");
            Console.WriteLine("✓ Custom validation passed");
        }
        catch (Exception ex)
        {
            Console.WriteLine($"Unexpected error: {ex.Message}");
        }

        // Invalid case
        try
        {
            Validator.Custom("abc", value => value.All(char.IsDigit), "Must contain only digits", "number");
        }
        catch (ValidationException ex)
        {
            Console.WriteLine($"✓ Custom validation failed as expected: {ex.Message}");
        }
    }

    // 6. Object validation
    public static void ObjectValidation()
    {
        Console.WriteLine("\n=== Object Validation ===");

        // Valid user creation
        try
        {
            var user = new User(
                "John Doe",
                "john.doe@example.com",
                30,
                new DateTime(1993, 5, 15),
                "+1234567890"
            );
            Console.WriteLine($"✓ Valid user created: {user}");
        }
        catch (Exception ex)
        {
            Console.WriteLine($"Unexpected error: {ex.Message}");
        }

        // Invalid user creation
        try
        {
            var invalidUser = new User(
                "", // Invalid name
                "invalid-email", // Invalid email
                -5, // Invalid age
                DateTime.Now.AddDays(1), // Invalid birth date
                "123" // Invalid phone
            );
        }
        catch (Exception ex)
        {
            Console.WriteLine($"✓ User validation failed as expected: {ex.Message}");
        }

        // Valid order creation
        try
        {
            var items = new List<OrderItem>
            {
                new OrderItem("Product 1", 2, 19.99m),
                new OrderItem("Product 2", 1, 29.99m)
            };
            var order = new Order(items, "customer@example.com");
            Console.WriteLine($"✓ Valid order created: {order}");
        }
        catch (Exception ex)
        {
            Console.WriteLine($"Unexpected error: {ex.Message}");
        }
    }

    // 7. Method with comprehensive validation
    public static void ProcessUserData(string name, string email, int age, string[] preferences)
    {
        Console.WriteLine("\n=== Processing User Data ===");

        try
        {
            // Validate input parameters
            Validator.NotNullOrWhiteSpace(name, nameof(name));
            Validator.Length(name, 2, 50, nameof(name));

            Validator.Email(email, nameof(email));

            Validator.InRange(age, 18, 120, nameof(age));

            Validator.NotNull(preferences, nameof(preferences));
            Validator.Count(preferences, 1, 10, nameof(preferences));

            foreach (var pref in preferences)
            {
                Validator.NotNullOrWhiteSpace(pref, nameof(preferences));
                Validator.Length(pref, 1, 50, nameof(preferences));
            }

            Console.WriteLine($"✓ Processing data for: {name} ({email}), Age: {age}");
            Console.WriteLine($"✓ Preferences: {string.Join(", ", preferences)}");

            // Process the data (simulation)
            Console.WriteLine("✓ User data processed successfully");
        }
        catch (Exception ex)
        {
            Console.WriteLine($"✗ Validation failed: {ex.Message}");
            throw;
        }
    }
}

class Program2
{
    static void Main(string[] args)
    {
        Console.WriteLine("=== C# Parameter Validation Examples ===\n");

        try
        {
            // Run all validation examples
            ValidationExamples.BasicValidation();
            ValidationExamples.StringValidation();
            ValidationExamples.CollectionValidation();
            ValidationExamples.DateValidation();
            ValidationExamples.CustomValidation();
            ValidationExamples.ObjectValidation();

            Console.WriteLine("\n=== Method Validation Examples ===");

            // Valid case
            try
            {
                ValidationExamples.ProcessUserData(
                    "Alice Smith",
                    "alice@example.com",
                    25,
                    new[] { "reading", "travel", "music" }
                );
            }
            catch (Exception ex)
            {
                Console.WriteLine($"Unexpected error in valid case: {ex.Message}");
            }

            // Invalid case
            try
            {
                ValidationExamples.ProcessUserData(
                    "", // Invalid name
                    "invalid-email", // Invalid email
                    15, // Invalid age
                    new string[] { } // Invalid preferences
                );
            }
            catch (Exception ex)
            {
                Console.WriteLine($"✓ Method validation failed as expected: {ex.Message}");
            }

            Console.WriteLine("\nAll parameter validation examples completed successfully!");
        }
        catch (Exception ex)
        {
            Console.WriteLine($"Unexpected error in main program: {ex.Message}");
        }
    }
}