**Course Title:** Mastering C#: From Fundamentals to Advanced Programming **Section Title:** Building Web Applications with ASP.NET Core **Topic:** Routing, controllers, and views in ASP.NET Core **Overview** In this topic, we'll explore the fundamentals of ASP.NET Core's routing, controllers, and views. You'll learn how to configure routing, create controllers and actions, and render views. By the end of this topic, you'll have a solid understanding of how to build robust web applications with ASP.NET Core. **What is Routing?** Routing is the process of mapping URLs to specific actions in your web application. It allows you to define a URL pattern that corresponds to a specific action, making it easier for users to navigate your application. **Configuring Routing** In ASP.NET Core, routing is configured in the `Startup.cs` file. The `Configure` method is where you define the routing configuration. ```csharp public void Configure(IApplicationBuilder app, IWebHostEnvironment env) { app.UseRouting(); app.UseEndpoints(endpoints => { endpoints.MapControllerRoute( name: "default", pattern: "{controller=Home}/{action=Index}/{id?}"); }); } ``` In this example, we're defining a default route that maps to the `Home` controller and the `Index` action. The `{id?}` parameter is optional. **Controllers** Controllers are the C in the MVC pattern. They handle user input, interact with the model, and return a view or a response. **Creating Controllers** To create a controller, you can inherit from the `Controller` class. ```csharp using Microsoft.AspNetCore.Mvc; using System; namespace MyApplication.Controllers { public class HomeController : Controller { public IActionResult Index() { return View(); } } } ``` In this example, we're creating a `HomeController` with an `Index` action that returns a view. **Actions** Actions are methods within controllers that handle specific HTTP requests. You can use a variety of attributes to decorate actions and define their behavior. ```csharp [HttpGet] public IActionResult Index() { return View(); } [HttpPost] public IActionResult Create([FromBody]MyModel model) { // Create a new model instance return RedirectToAction("Index"); } ``` In this example, we're defining two actions: `Index` and `Create`. The `Index` action handles GET requests, while the `Create` action handles POST requests. **Views** Views are the V in the MVC pattern. They represent the user interface of your application. **Creating Views** To create a view, you can create a `.cshtml` file in the `Views` folder. ```html @model MyModel @{ ViewData["Title"] = "Index"; } <h1>Index</h1> ``` In this example, we're creating a view that displays a title and a heading. **Layouts** Layouts are reusable views that contain the basic structure of your application. ```html @{ Layout = "_Layout"; } @section Scripts { <script src="~/js/myScript.js"></script> } ``` In this example, we're using the `_Layout` layout and defining a script section. **Key Concepts** * Routing is the process of mapping URLs to specific actions in your web application. * Controllers handle user input, interact with the model, and return a view or a response. * Actions are methods within controllers that handle specific HTTP requests. * Views represent the user interface of your application. **Practical Takeaways** * Use routing to define URL patterns that correspond to specific actions. * Create controllers and actions to handle user input and interact with the model. * Use views to represent the user interface of your application. * Define layouts to create reusable views that contain the basic structure of your application. **Additional Resources** * [ASP.NET Core Documentation: Routing](https://docs.microsoft.com/en-us/aspnet/core/fundamentals/routing?view=aspnetcore-6.0) * [ASP.NET Core Documentation: Controllers](https://docs.microsoft.com/en-us/aspnet/core/mvc/controllers/actions?view=aspnetcore-6.0) * [ASP.NET Core Documentation: Views](https://docs.microsoft.com/en-us/aspnet/core/mvc/views/overview?view=aspnetcore-6.0) We hope this topic has helped you understand the fundamentals of routing, controllers, and views in ASP.NET Core. If you have any questions or need further clarification, please leave a comment below. In the next topic, we'll cover working with Razor pages and form handling.