# C# Geliştirici İpuçları C# ile çalışan geliştiriciler için performans, okunabilirlik ve maintainability açısından önemli ipuçları ve best practice'ler. Bu yazıda deneyimli geliştiricilerin kullandığı teknikleri paylaşacağım. ## 1. Modern C# Özellikleri ### Null-conditional Operators ```csharp // Eski yöntem if (user != null && user.Profile != null && user.Profile.Address != null) { var city = user.Profile.Address.City; } // Modern yöntem var city = user?.Profile?.Address?.City; ``` ### Pattern Matching ```csharp // C# 8.0+ Switch Expressions public string GetDiscountType(decimal amount) => amount switch { < 100 => "No discount", >= 100 and < 500 => "Bronze", >= 500 and < 1000 => "Silver", >= 1000 => "Gold", _ => throw new ArgumentException("Invalid amount") }; // C# 11+ List Patterns public string AnalyzeNumbers(int[] numbers) => numbers switch { [] => "Empty array", [var x] => $"Single element: {x}", [var x, var y] => $"Two elements: {x}, {y}", [var first, .., var last] => $"Multiple elements: {first}...{last}", _ => "Unknown pattern" }; ``` ### Record Types ```csharp // Immutable record public record Person(string Name, int Age); // Mutable record public record PersonMutable { public string Name { get; set; } public int Age { get; set; } } // Usage var person = new Person("John", 30); var olderPerson = person with { Age = 31 }; // Creates new instance ``` ## 2. Performans İpuçları ### StringBuilder vs String Concatenation ```csharp // Yavaş - her concatenation'da yeni string oluşur string result = ""; for (int i = 0; i < 1000; i++) { result += $"Item {i}"; } // Hızlı - StringBuilder kullanımı var sb = new StringBuilder(); for (int i = 0; i < 1000; i++) { sb.Append($"Item {i}"); } string result = sb.ToString(); ``` ### Span ve Memory ```csharp // Heap allocation olmadan string slice ReadOnlySpan span = "Hello, World!".AsSpan(); ReadOnlySpan hello = span.Slice(0, 5); // "Hello" // Array işlemleri için Span kullanımı int[] numbers = { 1, 2, 3, 4, 5 }; Span span = numbers.AsSpan(); var slice = span.Slice(1, 3); // [2, 3, 4] ``` ### Async/Await Best Practices ```csharp // ConfigureAwait(false) kullanımı public async Task GetDataAsync() { var result = await httpClient.GetStringAsync(url) .ConfigureAwait(false); return result; } // ValueTask kullanımı - sıkça çağrılan metodlar için public ValueTask GetCachedValueAsync(string key) { if (_cache.TryGetValue(key, out var value)) return new ValueTask(value); // Synchronous completion return GetValueFromDatabaseAsync(key); // Asynchronous completion } ``` ## 3. LINQ İpuçları ### Performanslı LINQ Kullanımı ```csharp // Yavaş - multiple enumeration var numbers = GetNumbers(); var evenCount = numbers.Where(x => x % 2 == 0).Count(); var evenSum = numbers.Where(x => x % 2 == 0).Sum(); // Hızlı - single enumeration var evenNumbers = GetNumbers().Where(x => x % 2 == 0).ToList(); var evenCount = evenNumbers.Count; var evenSum = evenNumbers.Sum(); ``` ### Useful LINQ Extensions ```csharp public static class LinqExtensions { public static IEnumerable WhereNotNull(this IEnumerable source) where T : class { return source.Where(x => x != null)!; } public static IEnumerable<(T item, int index)> WithIndex(this IEnumerable source) { return source.Select((item, index) => (item, index)); } public static void ForEach(this IEnumerable source, Action action) { foreach (var item in source) action(item); } } // Kullanım var names = new[] { "John", null, "Jane", null }; var validNames = names.WhereNotNull().WithIndex(); ``` ## 4. Exception Handling ### Custom Exceptions ```csharp public class BusinessException : Exception { public string ErrorCode { get; } public object? Details { get; } public BusinessException(string message, string errorCode, object? details = null) : base(message) { ErrorCode = errorCode; Details = details; } } // Usage if (user.Balance < amount) { throw new BusinessException( "Insufficient balance", "INSUFFICIENT_BALANCE", new { CurrentBalance = user.Balance, RequestedAmount = amount } ); } ``` ### Global Exception Handler ```csharp public class GlobalExceptionMiddleware { private readonly RequestDelegate _next; private readonly ILogger _logger; public GlobalExceptionMiddleware(RequestDelegate next, ILogger logger) { _next = next; _logger = logger; } public async Task InvokeAsync(HttpContext context) { try { await _next(context); } catch (Exception ex) { _logger.LogError(ex, "An unhandled exception occurred"); await HandleExceptionAsync(context, ex); } } private async Task HandleExceptionAsync(HttpContext context, Exception exception) { context.Response.ContentType = "application/json"; var response = exception switch { BusinessException businessEx => new { StatusCode = 400, Message = businessEx.Message, ErrorCode = businessEx.ErrorCode }, NotFoundException => new { StatusCode = 404, Message = "Resource not found" }, _ => new { StatusCode = 500, Message = "An internal server error occurred" } }; context.Response.StatusCode = response.StatusCode; await context.Response.WriteAsync(JsonSerializer.Serialize(response)); } } ``` ## 5. Dependency Injection Patterns ### Service Lifetimes ```csharp // Startup.cs veya Program.cs services.AddSingleton(); services.AddScoped(); services.AddTransient(); // Factory Pattern services.AddScoped(); services.AddScoped>(provider => serviceType => { return serviceType switch { ServiceType.Email => provider.GetService(), ServiceType.Sms => provider.GetService(), _ => throw new ArgumentException($"Unknown service type: {serviceType}") }; }); ``` ### Options Pattern ```csharp public class EmailSettings { public string SmtpServer { get; set; } = string.Empty; public int Port { get; set; } public string Username { get; set; } = string.Empty; public string Password { get; set; } = string.Empty; } // Registration services.Configure(configuration.GetSection("EmailSettings")); // Usage public class EmailService { private readonly EmailSettings _settings; public EmailService(IOptions options) { _settings = options.Value; } } ``` ## 6. Testing İpuçları ### Unit Test Best Practices ```csharp [TestClass] public class UserServiceTests { private Mock _userRepositoryMock; private UserService _userService; [TestInitialize] public void Setup() { _userRepositoryMock = new Mock(); _userService = new UserService(_userRepositoryMock.Object); } [TestMethod] public async Task GetUserAsync_ValidId_ReturnsUser() { // Arrange var userId = 1; var expectedUser = new User { Id = userId, Name = "John" }; _userRepositoryMock .Setup(x => x.GetByIdAsync(userId)) .ReturnsAsync(expectedUser); // Act var result = await _userService.GetUserAsync(userId); // Assert Assert.IsNotNull(result); Assert.AreEqual(expectedUser.Name, result.Name); _userRepositoryMock.Verify(x => x.GetByIdAsync(userId), Times.Once); } } ``` ### Integration Tests ```csharp [TestClass] public class UserControllerIntegrationTests { private WebApplicationFactory _factory; private HttpClient _client; [TestInitialize] public void Setup() { _factory = new WebApplicationFactory(); _client = _factory.CreateClient(); } [TestMethod] public async Task GetUser_ValidId_ReturnsUser() { // Arrange var userId = 1; // Act var response = await _client.GetAsync($"/api/users/{userId}"); // Assert response.EnsureSuccessStatusCode(); var content = await response.Content.ReadAsStringAsync(); var user = JsonSerializer.Deserialize(content); Assert.IsNotNull(user); } } ``` ## 7. Memory Management ### IDisposable Pattern ```csharp public class ResourceManager : IDisposable { private bool _disposed = false; private readonly FileStream _fileStream; private readonly Timer _timer; public ResourceManager(string filePath) { _fileStream = new FileStream(filePath, FileMode.Open); _timer = new Timer(TimerCallback, null, 0, 1000); } public void Dispose() { Dispose(true); GC.SuppressFinalize(this); } protected virtual void Dispose(bool disposing) { if (!_disposed) { if (disposing) { _fileStream?.Dispose(); _timer?.Dispose(); } _disposed = true; } } ~ResourceManager() { Dispose(false); } } ``` ### Using Statements ```csharp // Traditional using using (var stream = new FileStream("file.txt", FileMode.Open)) { // Process file } // Using declaration (C# 8.0+) using var stream = new FileStream("file.txt", FileMode.Open); // Stream automatically disposed at end of scope ``` ## 8. Configuration ve Environment ### Structured Configuration ```csharp public class ApplicationSettings { public DatabaseSettings Database { get; set; } = new(); public EmailSettings Email { get; set; } = new(); public ApiSettings Api { get; set; } = new(); } public class DatabaseSettings { public string ConnectionString { get; set; } = string.Empty; public int CommandTimeout { get; set; } = 30; } // appsettings.json { "ApplicationSettings": { "Database": { "ConnectionString": "Server=localhost;Database=MyDb;", "CommandTimeout": 60 }, "Email": { "SmtpServer": "smtp.gmail.com", "Port": 587 } } } ``` ## Sonuç Bu ipuçları, C# ile daha verimli ve maintainable kod yazmanızı sağlayacak. Özellikle: - **Modern C# özelliklerini** kullanarak kodu daha okunabilir hale getirin - **Performans optimizasyonlarını** ihmal etmeyin - **LINQ'u** doğru şekilde kullanın - **Exception handling** stratejinizi belirleyin - **Dependency injection** pattern'larını öğrenin - **Testing** kültürünü benimseyin - **Memory management** konusunda dikkatli olun Bu teknikleri projelerinizde uyguladığınızda, kodunuzun kalitesinde büyük bir artış göreceksiniz.

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C# Geliştirici İpuçları