.NET Developer Guide

In this article, I’ll walk you through the top 10 .NET coding best practices that every developer should follow. Along the way, I’ll provide clear examples of what to do and what to avoid to help you write clean, maintainable, and professional-grade code.

1. Meaningful Naming

✅ Good Example

Names should convey intent and functionality clearly.
Follow naming conventions (PascalCase for classes and methods).
The method’s purpose should be clear from its name, without needing to inspect the implementation.

public class CustomerOrderProcessor
{
    public void ProcessOrder(Order order)
    {
        if (order.IsValid())
        {
            SaveOrder(order);
            SendOrderConfirmationEmail(order);
        }
    }

    private void SaveOrder(Order order) 
    { 
         // Logic goes here
    }

    private void SendOrderConfirmationEmail(Order order) 
    { 
        // Logic goes here
    }
}

❌ Bad Example

Uses vague abbreviations like “Proc”, “Save”, or “Email” that don’t clearly explain what the method does.
Ignores naming conventions and lacks meaningful context.
Makes code hard to read, maintain, and extend.

public class CstOrdProcess
{
    public void Proc(Order o)
    {
        if (o.ok())
        {
            Save(o);
            Email(o);
        }
    }

    private void Save(Order o) 
    {
	     // Code goes here 
    }

    private void Email(Order o) 
    { 
        // Code gies here 
    }
}

2. Avoid Magic Numbers and Strings

✅ Good Example

Uses named constants or enum that provide context.
Makes the code easier to understand at a glance.
Simplifies maintenance when values need to change.

public const int MaxRetryCount = 5;
if (retryAttempts > MaxRetryCount)
{ 

  // Add logic here
  
}

public enum OrderStatus
{
    Pending,
    Shipped,
    Cancelled
}

if (order.Status == OrderStatus.Shipped)
{
    // Proceed with delivery
}

❌ Bad Example

Uses raw numbers or strings with no explanation.
Forces others to guess the meaning or check documentation.
Increases risk of bugs if values are used inconsistently.

if (retryAttempts > 5)  //  ❌ Avoid Magic number
{ 
 //* handle *// 
}

if (order.Status == "S") // What is "S"? Shipped? Submitted?
{
    // Proceed with delivery
}

3. Keep Methods Short and Focused

✅ Good Example

Each method does one thing and is clearly named.
Easier to test, read, and reuse.
Easy to isolate bugs or update logic.

public void ProcessOrder(Order order)
{
    ValidateOrder(order);  // perform validation
    SaveOrder(order);      // Save order details to database
    SendConfirmation(order); // Send notification
}
private void ValidateInvoice(Invoice invoice)
{
    // Perform validation logic here
}

private void SaveInvoice(Invoice invoice)
{
    // Save to database
}

private void SendInvoiceEmail(Invoice invoice)
{
    // Send confirmation email
}

❌ Bad Example

Validation, persistence, and communication logic are all bundled into one method.
Hard to read, test, and maintain.
Violates the Single Responsibility Principle (SRP).

public void ProcessOrder(Order order)
{
    if (order.Total <= 0) 
    {
        throw new Exception("Invalid order");
    }
    // Code for validation 20 lines
    // Code for save order 50 lines
    // code for send notification 30 lines
    // ... 100 more lines
}

4. Handle Exceptions Gracefully

✅ Good Example

Logs with context
- Example: Log the OrderId and any related metadata when an exception occurs during order processing
Catches specific exceptions first
- Example: Catch ValidationException or SqlException separately before using a general catch (Exception) block.
Preserve the Stack Trace by Rethrowing Exceptions Properly
- Avoid using throw ex;, it resets the stack trace and makes debugging much harder.

public async Task ProcessOrderAsync(Order order)
{
    try
    {
        await _orderService.ProcessOrderAsync(order);
    }
    catch (ValidationException ex)
    {
        _logger.LogWarning(ex, "Validation failed for order {OrderId}", order.Id);
        throw; 
        // rethrow for higher-level handling
    }
    catch (Exception ex)
    {
        _logger.LogError(ex, "Unexpected error while processing order {OrderId}", order.Id);
        throw; 
        // never swallow general exceptions
    }
}

❌ Bad Example

Silently Swallowing Exceptions
- If something goes wrong and you suppress the error without handling or logging it, your application may continue running in an unstable or incorrect state.
Lack of Logging or User Feedback
- Always log exceptions with meaningful messages and relevant data to aid support and diagnostics.
Using throw ex; Resets the Stack Trace
- Avoid using throw ex;, it resets the stack trace and makes debugging much harder.

public void ProcessOrder(Order order)
{
    try
    {
        _orderService.ProcessOrder(order);
    }
    catch
    {
        // Silent catch — exception is lost, no logging, impossible to debug
    }
}

5. Use Dependency Injection

✅ Good Example

Uses constructor injection, the most common and test-friendly form of DI.
Depends on an interface, not a concrete implementation—making it easy to mock in unit tests.
Promotes loose coupling and open/closed principle from SOLID.

public interface INotificationService
{
    void Send(string message);
}

public class OrderProcessor
{
    private readonly INotificationService _notificationService;

    public OrderProcessor(INotificationService notificationService)
    {
        _notificationService = notificationService;
    }

    public void Process(Order order)
    {
        // process the order...
        _notificationService.Send("Order processed successfully.");
    }
}

❌ Bad Example

Tightly couples OrderProcessor to a specific NotificationService implementation.
Harder to test (requires the real service instead of a mock/stub).
Violates Inversion of Control and makes the code less flexible and harder to maintain.

public class OrderProcessor
{
    private readonly NotificationService _notificationService = new NotificationService();

    public void Process(Order order)
    {
        // process the order...
        _notificationService.Send("Order processed successfully.");
    }
}

6. Use `async` and `await` properly

✅ Good Example

Uses async/await correctly for non-blocking operations.
Returns Task or Task<T> from async methods.
Avoids deadlocks by not mixing synchronous waits with async code.

public async Task<string> GetUserDataAsync(int userId)
{
    var response = await _httpClient.GetAsync($"https://api.example.com/users/{userId}");
    response.EnsureSuccessStatusCode();
    
    return await response.Content.ReadAsStringAsync();
}

❌ Bad Example

Using .Result blocks the thread instead of running asynchronously with await, which can lead to deadlocks in UI or ASP.NET applications.
It goes against the purpose of async programming, which is to keep operations non-blocking.
This approach doesn’t scale well under load, as it ties up threads that could be used elsewhere.

public string GetUserData()
{
    // Blocking async code with .Result — can cause deadlocks in ASP.NET, UI apps
    var response = _httpClient.GetAsync("https://api.example.com/user/1").Result;
    var content = response.Content.ReadAsStringAsync().Result;
    return content;
}

7. Use Logging Effectively

✅ Good Example

Logs contain meaningful context (e.g., user ID, order ID, exception details).
Uses appropriate log levels (Information, Warning, Error, etc.).
Avoids logging sensitive data (like passwords or tokens).

try
{
    var result = await _paymentService.ProcessAsync(orderId);
    _logger.LogInformation("Payment processed successfully for OrderId: {OrderId}", orderId);
}
catch (PaymentException ex)
{
    _logger.LogWarning(ex, "Payment failed for OrderId: {OrderId}", orderId);
}
catch (Exception ex)
{
    _logger.LogError(ex, "Unexpected error while processing OrderId: {OrderId}", orderId);
    throw;
}

✅ Benefits:

Helps identify and reproduce issues.
Provides structured, searchable logs.
Maintains security and clarity.

❌ Bad Example

Uses unclear or generic log messages.
Misses important details needed to understand the issue.
Logs too much, too little, or always uses the wrong log level.
Includes sensitive data that shouldn’t be logged.

try
{
    ProcessPayment(order);
}
catch (Exception ex)
{
   // ❌ No context
   _logger.LogError("Something went wrong."); 
    
   // ❌ Sensitive data risk:
   // _logger.LogError("Card number: {0}", order.CardNumber); 
}

8. Apply SOLID Principles

✅ Good Example – Follows SRP & DIP

Each class does one thing and does it well.
Dependencies are abstracted, supporting the Open/Closed and Dependency Inversion principles.
Easy to test, mock, and extend without changing core logic.

❌ Bad Example

Handles too many responsibilities (validation, DB access, process logic).
Tightly coupled to infrastructure (SQL connection string hardcoded).
Violates Single Responsibility and Dependency Inversion.
Difficult to test in isolation.

public class OrderProcessor
{
    public void Process(Order order)
    {
        if (order.Total <= 0 || !order.Items.Any())
            throw new Exception("Invalid order");

        using (var connection = new SqlConnection("connectionString"))
        {
            // Logic to Save to DB directly
        }

        Console.WriteLine("Order processed successfully");
    }
}

9. Use Null Safety and Guard Clauses

✅ Good Example

Fails fast with clear error messages.
Reduces nested code by returning early.
Prevents null reference exceptions.
Makes logic easier to read and maintain.

public class UserService
{
    public void CreateUser(User user)
    {
        // Validate user before order process
        ValidateUser(user);

        // Proceed with creating user
        SaveToDatabase(user);
    }

    private void SaveToDatabase(User user)
    {
        // Save logic here
    }
    
    private void ValidateUser(User user)
    {
         if (user == null)
            throw new ArgumentNullException(nameof(user));

        if (string.IsNullOrWhiteSpace(user.Email))
            throw new ArgumentException("Email cannot be empty.", nameof(user.Email));
    }
}

// Responsibility: validate orders
public interface IOrderValidator
{
    bool IsValid(Order order);
}

// Implement IOrderValidator and define logic for order validation
public class OrderValidator : IOrderValidator
{
    public bool IsValid(Order order) => order.Total > 0 && order.Items.Any();
}

// Responsibility: store orders
public interface IOrderRepository
{
    void Save(Order order);
}

//Implement IOrderRepository
public class SqlOrderRepository : IOrderRepository
{
    public void Save(Order order)
    {
        // Save to database logic
    }
}

// Responsibility: orchestrate order processing
public class OrderService
{
    private readonly IOrderValidator _validator;
    private readonly IOrderRepository _repository;

    public OrderService(IOrderValidator validator, IOrderRepository repository)
    {
        _validator = validator;
        _repository = repository;
    }

    public void ProcessOrder(Order order)
    {
        if (!_validator.IsValid(order))
            throw new InvalidOperationException("Invalid order.");

        _repository.Save(order);
    }
}

❌ Bad Example

No input validation — user or user.Email could be null.
May cause runtime exceptions that are hard to trace.
Logic continues even if data is invalid.
Lacks clear error handling.

public class UserService
{
    public void CreateUser(User user)
    {
        // ❌ Assumes user never null
	    // When the user is null the below code will throw an error
        SaveToDatabase(user);

         // ❌ Assumes user email is never null
  	     // When the user's email is null, then the below code will throw an error

        SendWelcomeEmail(user.Email.ToLower());
    }

    private void SaveToDatabase(User user)
    {
        // Save logic
    }

    private void SendWelcomeEmail(string email)
    {
        // Email logic
    }
}

10. Use Modern C# and .NET Features

✅ Good Example: (C# 12 Primary Constructor):

public class ProductService(ILogger<ProductService> _logger)
{
    public void Log() => _logger.LogInformation("Service started.");
}

❌ Bad Example

While still correct, the older style is now less concise and expressive with newer syntax available.

public class ProductService
{
    private readonly ILogger<ProductService> _logger;

    public ProductService(ILogger<ProductService> logger)
    {
        _logger = logger;
    }
}

✅ Summary: .NET Best Practices Every Developer Should Follow in 2025

This article covers the top .NET coding best practices for 2025 to help developers write clean, scalable, and maintainable code. It focuses on clear naming, concise methods, SOLID principles, proper exception handling, and smart use of dependency injection.

It also highlights modern .NET features like async/await, structured logging, and nullable reference types, along with tips on configuration, immutability, and service lifetimes helping teams build reliable, professional-grade applications.

I’ll be sharing more valuable tips in Part 2 of this article soon. Stay tuned to further enhance your .NET skills, and feel free to share your feedback to help improve future content.

3. Keep Methods Short and Focused

4. Handle Exceptions Gracefully

5. Use Dependency Injection

6. Use async and await properly

❌ Bad Example

7. Use Logging Effectively

✅ Benefits:

❌ Bad Example

8. Apply SOLID Principles

✅ Good Example – Follows SRP & DIP

❌ Bad Example

9. Use Null Safety and Guard Clauses

✅ Good Example

❌ Bad Example

10. Use Modern C# and .NET Features

✅ Good Example: (C# 12 Primary Constructor):

❌ Bad Example

6. Use `async` and `await` properly