Attribute Routing Overview | MVC | .NET Core

Attribute routing in ASP.NET Core allows you to define routes directly on controller actions using attributes. This provides precise control over routing, enabling complex scenarios with route parameters, optional values, constraints, and combined routes, enhancing clarity and flexibility in your API design.

In ASP.NET Core, attribute routing is a powerful feature that allows you to specify routing information directly on controller actions. This provides greater flexibility and control over the routing of HTTP requests to your API endpoints compared to conventional routing.

Here’s an overview of how attribute routing works and how to use it effectively in your .NET Core API.

What is Attribute Routing?

Attribute routing enables you to define routes directly on your action methods or controllers using attributes. This approach is more explicit and can make routing more understandable and manageable.

How to use Attribute Routing?

1. Basic Attribute Routing

You can apply routing attributes directly to action methods and controllers. For example.

[ApiController]
[Route("api/[controller]")]
public class ProductsController : ControllerBase
{
    // GET api/products
    [HttpGet]
    public IActionResult GetAllProducts()
    {
        // Implementation
    }
    // GET api/products/5
    [HttpGet("{id}")]
    public IActionResult GetProductById(int id)
    {
        // Implementation
    }
    // POST api/products
    [HttpPost]
    public IActionResult CreateProduct([FromBody] Product product)
    {
        // Implementation
    }
}

• Controller Route: [Route("api/[controller]")] sets the base route for all actions in the controller. [controller] is a placeholder that gets replaced with the name of the controller (e.g., Products).
• Action Routes: [HttpGet], [HttpGet("{id}")], [HttpPost] specify the HTTP methods and the routes for the actions.

2. Route Parameters

You can use route parameters in the attribute routing to capture values from the URL.

[HttpGet("search/{query}")]
public IActionResult SearchProducts(string query)
{
    // Implementation
}

Route Parameter: {query} in the route template will capture the value from the URL and pass it to the action method.

3. Optional Parameters

To make route parameters optional, use the following syntax.

[HttpGet("items/{id?}")]
public IActionResult GetItemById(int? id)
{
    // Implementation
}

Optional Parameter: {id?} makes the id parameter optional.

4. Route Constraints

You can add constraints to route parameters to enforce specific patterns.

[HttpGet("products/{id:int}")]
public IActionResult GetProductById(int id)
{
    // Implementation
}

Route Constraint: {id:int} ensures that the id parameter must be an integer.

5. Route Prefixes and Constraints at Controller Level

You can also set route prefixes and constraints at the controller level.

[ApiController]
[Route("api/[controller]/[action]")]
public class OrdersController : ControllerBase
{
    [HttpGet]
    public IActionResult GetAllOrders()
    {
        // Implementation
    }

    [HttpGet("{id:int}")]
    public IActionResult GetOrderById(int id)
    {
        // Implementation
    }
}

Action Route: [action] is replaced with the action method name in the route URL.

6. Combining Routes

You can combine routes and use route templates to create complex routing scenarios.

[ApiController]
[Route("api/[controller]")]
public class CustomersController : ControllerBase
{
    [HttpGet("{customerId}/orders/{orderId}")]
    public IActionResult GetCustomerOrder(int customerId, int orderId)
    {
        // Implementation
    }
}

Benefits of Attribute Routing

• Clarity and Control: Route definitions are more explicit and closely related to their corresponding actions, making it easier to understand and manage routes.
• Flexibility: Allows for more complex routing scenarios, including optional and default parameters, constraints, and combined routes.
• Customization: Facilitates precise control over route templates and endpoints.

Combined Route

The route combines customerId and orderId parameters to define a more specific endpoint.