🧭 Start with Structure and Consistency
When building Web APIs in ASP.NET Core, clarity and consistency are key.
Start by using the [ApiController] attribute to automatically handle model validation and binding behavior. Stick to clear RESTful routing conventions such as:
GET /api/v1/products
POST /api/v1/products
GET /api/v1/products/{id}
PUT /api/v1/products/{id}
DELETE /api/v1/products/{id}
Version your endpoints using route segments like /api/v1/controller so you can evolve your API without breaking existing clients.
🧼 Keep Your Controllers Thin
Avoid placing business logic inside controllers. Instead, delegate to well-defined service classes. Keep each controller responsible for handling the request and passing it to the appropriate service or use case.
Group code by features using feature folders and follow Clean Architecture principles to separate concerns clearly. This results in more scalable and testable codebases.
✅ Validate with FluentValidation
Use the FluentValidation library to enforce validation rules outside your models. Register validators with dependency injection and keep controller code focused only on what it must do.
Validation failures are automatically handled when [ApiController] is used, which keeps your endpoints clean.
🛑 Handle Errors with Grace
Use the new global exception handling approach via IExceptionHandler in .NET 8 and above. Avoid try-catch blocks inside controllers.
Return errors using ProblemDetails, a standardized error response format that is easy for clients to parse.
🔐 Secure Your APIs Properly
Implement JWT Bearer Authentication and protect endpoints using the [Authorize] attribute. Always use Role-Based Access Control (RBAC) where necessary to restrict sensitive operations to specific user roles.
Avoid hardcoded secrets and sensitive configuration in source code. Use appsettings.json and bind settings using the Options Pattern.
💉 Use Dependency Injection Effectively
ASP.NET Core has built-in support for dependency injection. Register services with the correct lifetimes, such as scoped for application services and always depend on interfaces rather than concrete classes.
Group service registrations with extension methods to keep Program.cs clean and organized.
🔄 Handle Data the Right Way
Do not expose EF Core entities directly through your APIs. Use Data Transfer Objects (DTOs) to shape data and prevent over-posting or data leaks.
Always use AsNoTracking() in read-only queries to improve performance. Make all database operations async and await properly.
📈 Monitor and Optimize
Enable health checks to verify your service is alive and responsive. Add rate limiting to protect against abuse.
Integrate Serilog for structured logging. Use multiple sinks like console, file or Elasticsearch to capture logs in different environments. Avoid logging sensitive data such as passwords or credit card numbers.
Redirect all HTTP requests to HTTPS and enforce secure transport to protect data in transit.
📦 Return Consistent Results
Use ActionResult<T> in your controller methods to maintain consistency with HTTP status codes and return values. This improves readability and ensures correct response formatting.
Example:
[HttpGet("{id}")]
public async Task<ActionResult<ProductDto>> GetById(Guid id)
{
var product = await _service.GetByIdAsync(id);
if (product == null) return NotFound();
return Ok(product);
}
🧩 Final Thoughts
Following these best practices will help you build APIs that are secure, scalable and easy to maintain. Whether you are working on a small internal project or a public-facing API used by thousands, structure and discipline make a difference.
Start small, stay clean, grow with confidence.