Working with Areas & IActionResult

1. Description

Areas are a way to partition an ASP.NET Core MVC app into logical sections (e.g., Admin, Shop) each with its own controllers, views, and routes. IActionResult is the common return type for controller actions; it represents various result types like ViewResult, RedirectResult, JsonResult, etc.

2. Why It Is Important

Areas help organize large apps and group related functionality. Returning IActionResult gives flexibility to return different result types from the same action (view, redirect, file, JSON), which is useful for API endpoints and UI controllers.

3. Real-World Examples

• An Admin area containing dashboard controllers and views segregated from public site code.
• Actions that sometimes return a view or sometimes return NotFound() for missing resources.

4. Syntax & Explanation

Area folder structure (convention):

• Areas/
  • Admin/
    • Controllers/
    • Views/
    • AdminAreaRegistration (not required in Core)

Controller in an area:

using Microsoft.AspNetCore.Mvc;

[Area("Admin")]
public class DashboardController : Controller
{
    public IActionResult Index()
    {
        return View(); // returns ViewResult
    }

    public IActionResult Details(int id)
    {
        var model = GetModel(id);
        if (model == null) return NotFound(); // returns NotFoundResult
        return View(model);
    }

    [HttpPost]
    public IActionResult Save(MyModel m)
    {
        if (!ModelState.IsValid) return BadRequest(ModelState);
        // save
        return RedirectToAction("Index"); // RedirectToActionResult
    }
}

Routing to an area (by default): /Admin/Dashboard/Index

Common IActionResult types:

• View() / View(model) → render a view.
• RedirectToAction(...) → redirect.
• Json(object) → JSON result.
• File(...) → serve a file.
• NotFound() / BadRequest() / Ok() → status results.

5. Use Cases

• Separate admin functionality from public website code.
• Return different HTTP responses based on validation or resource state.
• Serve files, JSON, or views from the same controller depending on context.

6. Mini Practice Task

1. Create an Admin area with a UsersController and an Index view that lists users.
2. Implement an action that returns NotFound() when an ID is missing and View(model) otherwise.