In ASP .NET MVC (Model-View-Controller) is one of the best features that help to define routings redirects URLs to controllers and actions. This mechanism is crucial in addressing the common problem of a sloppy, SEO-compliant, and user-friendly URL structure for web apps. Custom routing enables the developer to go beyond the simple route template and come up with more meaningful URLs that would be easily understood by users as well as giving the application more richness in terms of functionality. 

Understanding MVC Routing 

By default, MVC uses convention-based routing, which follows a standard pattern: To this point, the URL routing used for any site must use the following format: >>{controller}/{action}/{id} This default routing is quite convenient for basic application, but while developing more complex or more extensive applications, a router offers more options and opportunities. 

Custom routing simplifies the possibility of presenting more meaningful URLs based on using developers. For instance, rather than URLs such as /Products/Details/1, it is possible to set up the routes that yield URLs like /shop/products/1. 

The basic routing in MVC is based on RouteConfig .Cs file. Located at App_Start it contains the setting for matching a particular URL to a specific controller action. When a user types in a URL, the routing engine takes the URL and puts it through a parser before it determines which controller and action must be called according to this routing configuration file. 

For example, a basic route configuration looks like this:

• routes.MapRoute(
• name: "Default",
• url: "{controller}/{action}/{id}",
• defaults: new { controller = "Home", action = "Index", id = UrlParameter.Optional }
• );

 This default pattern takes the URL with the expectation of controller, action, and the id. However, this pattern may not be adequate in serving your application’s requirement and that is where ‘Custom Routing’ comes into play. 

Implementing Custom Routing 

Thus, for a specific scenario in your application, custom routes can be created to match specific patterns. Here are key steps to implement custom routing:

1. Define Specific URL Patterns: Instead of using global URLs, where defined patterns that are meaningful are permitted by custom routes. For instance, within the context of constructing an e-commerce software, one does not have to call a path ‘/login’ even as the real capability is extra carefully related to the commercial enterprise common sense of the platform. A custom course would possibly look like this: 

• routes.MapRoute(
• name: "ProductDetails",
• url: "shop/products/{id}",
• defaults: new { controller = "Products", action = "Details", id = UrlParameter.Optional }
• );

This particular custom route enables the users to be able to browse the website using URL strings such as /shop/products/12 instead of /Products/Details/12. 

2. Multiple Routes for Different Scenarios: There are different ways of defining these routes based on the structure of the URLs. For example, one route could be for products and another for services:

• routes.MapRoute(
• name: "Services",
• url: "our-services/{id}",
• defaults: new { controller = "Services", action = "Details", id = UrlParameter.Optional }
• );

This gives room for an acceptable URL appearance, which is useful for the users in their search. 

3. Attribute-Based Routing: In the MVC 5, Microsoft has brought out a new approach to defining routes called attribute-based routing. Thus the proposed solution is a change of strategy such that, instead of relying on the centralized RouteConfig. Cs, routes can be declared directly on a controller actions using attributes. This brings some level of control in managing routes, especially in large applications where the controllers are defined in a way that they have their unique URL architecture. Here’s a simple example of attribute routing:

• [Route("shop/products/{id}")]
• public ActionResult Details(int id) {
• // Controller logic
• }

This method is more flexible and easier to sustain in complicated endeavors since routes are proximal to the controllers. 

4. Route Constraints: At other times, however, you might need to pass criteria to your custom routes that will limit them to specific parameters in the URLs. For instance, if the ID in the URL should only accept numeric values, you can apply a constraint: 

• routes.MapRoute(
• name: "ProductDetails",
• url: "shop/products/{id}",
• defaults: new { controller = "Products", action = "Details" },
• constraints: new { id = @"\d+" } // Ensures ID is numeric
• );

This eliminates the possibility of the application of the route to any just any invalid URLs while the extra layer of control allows for its application to only valid URLs that the application recognizes.

Benefits of Custom Routing 

1. SEO-Friendly URLs: Custom routes enable one to define clean URLs that are easy to index by Search Engine Bots. For instance, links such as /shop/products/laptop look and are much better for SEO than Links like /Products/Details/1. 

2. Enhanced User Experience: Here, GUI URLs or easily understandable URLs help the users to navigate around the application while they do not need to know every step of the application. 

3. Increased Flexibility: Custom routes, in my point of view, give much liberty because they allow you to set up special URL paths for different parts of your application. This is especially useful in systems that are comprised of several modules, for instance, e-shops where products, categories, and users have URLs in different formats. 

4. Modular Design: When the number of custom routes is set into one route different segments of the application can be separated and arranged more efficiently. This modular approach of laying down the structure not only enhances the navigation system of the application but also enhances the management of the adding-on process as the application evolves. 

Best Practices for Custom Routing

1. Plan Your URL Structure: Before defining specific routes then organize the structure of URLs. Think about how users will approach your application as well as the URL patterns that will simplify the user experience. 

2. Use Attribute Routing for Complex Scenarios: When the controllers can contain many actions that may have different URL patterns, attribute routing can assist you in grouping nice routes near the specific action methods​. 

3. Test Thoroughly: After setting up custom routes, always take some time to check them against the intended URLs, and viewing incorrect URLs should lead to an appropriate error message. 

4. Avoid Overcomplicating Routes: Custom routing is effective, yet Don’t put too many levels of routing that are difficult, confusing, and hard to manage. Each site should have a simple, clear structure, or else its accessibility for a programmer will not be as good while intended users might find the routes shown confusing. 

Conclusion 

Custom routing in MVC goes a long way in handling the URLs of an application, therefore, instilling the best and convenient practices that aid in the improvement of SEO friendliness of the application paths for enhanced usability. Regardless, of which of the methods you choose, which is traditional in RouteConfig.cs or the more modern attribute-based approach, custom routing is one of the tools that can not be ignored in the MVC framework to ensure that your web application meets both business and technical needs.