Lecture 24: Advanced GET Filtering with Business Rules
REST API Development: Build, Test, Troubleshoot
In this lecture, we explore advanced techniques for filtering GET requests using business rules.
These methods allow your API to return highly specific datasets tailored to the client’s needs.
Why Advanced Filtering is Important
Basic GET queries may return all records or simple filters by ID or category. Advanced filtering
enables your API to enforce business logic and reduce unnecessary data transfer.
- Enforce business rules directly on the server
- Reduce client-side processing by returning only relevant data
- Improve API performance and response times
- Provide more meaningful and actionable results to clients
Example: Filtering by Business Rules
Suppose you have an e-commerce API. You can filter products based on stock, category, and
discount eligibility in one GET request:
GET /api/products?category=electronics&inStock=true&discountEligible=true
This request returns only electronics that are in stock and eligible for discounts,
allowing the client to display relevant products immediately.
Implementing Advanced GET Filtering in ASP.NET Core
[HttpGet]
public IActionResult GetProducts([FromQuery] string category, [FromQuery] bool inStock, [FromQuery] bool discountEligible)
{
var products = _db.Products.AsQueryable();
if(!string.IsNullOrEmpty(category))
products = products.Where(p => p.Category == category);
if(inStock)
products = products.Where(p => p.Stock > 0);
if(discountEligible)
products = products.Where(p => p.IsDiscountEligible);
return Ok(products.ToList());
}
Using query parameters and conditional filtering ensures the API applies business rules efficiently.
Best Practices
- Use query parameters for optional filters
- Keep filtering logic on the server to maintain data consistency
- Document all available filters and their effects
- Test combinations of filters to ensure correct results
Conclusion
Advanced GET filtering empowers your API to return precise, rule-based results.
Implementing these techniques improves performance, enforces business logic, and enhances the client experience.