From Pluralsight/ASP.NET Core 6 Fundamentals

Overview

A view is an HTML template as a .cshtml file with embedded Razor markup (code that interactions w/HTML to render a page).

Views handle data presentation and user interaction.
Views are organized like this where each folder on Views/ is named for each of the app’s controllers:
- In Views/Home, when a user requests either Index, Contact, or About, the Home controller determines which of the views is used to build and return that page to the user.

Layouts

Layouts provide consistent web page sections (like header, footer, navigation/menu).

View Responsibilities

Present content through the UI so it can be processed by a controller action.
Contains minimal logic, and the logic they do contain is related to presenting content.

Conditions, loops
Tag helpers, view components

The view is a template (cshtml) that contains markup to visualize the data of the model.
Server-side code will generate HTML which will be sent to the client.

For every controller, a corresponding subfolder of that controller’s name is created under /Views.

For example, if /Controllers/PieControllers.cs, then /Views/Pie/ and for each action, an action-name.cshtml file.

A basic View:

<!DOCTYPE html>

<html>
    <head>
        <title>Index</title>
    </head>
    <body>
        <div>
            @ViewBag.Message
        </div>
    </body>
</html>

A strongly-typed View involves passing a model to the View and the View accesses the model’s properties:

@model IEnumerable<Pie> // include the type of object being passed in
<html>
    <body>
    <div>
        @foreach (var pie in Model) // the model is accessed via Model
        {
        <div>
        <h2>@pie.Name</h2>
        <h3>@pie.Price.ToString("c")</h3>
        <h4>@pie>Category.CategoryName</h4>
        </div>
        }
    </div>
    </body>
</html>

ViewModel Responsibilities

When a Model we want to pass to a View does not map to a domain model, use a ViewModel.
A ViewModel is a class that wraps multiple properties so that the View can access the data it needs. It is a model for the view. ViewModels are not entities that live in the database. They are stored under /ViewModels by convention.

public class PieListViewModel
{
	public IEnumerable<Pie>? Pies { get; set; }
	public string? CurrentCategory { get; set; }
}

Creating a View

Views that are specific to a controller are placed in Views/ControllerName. Views that are shared are placed in Views/Shared.

This is Views/Home/About.cshtml:

@{
    ViewData["Title"] = "About";
}

<h2>@ViewData["Title"].</h2>
<h3>@ViewData["Message"]</h3>

<p>Use this area to provide additional information.</p>

Returning Views in Controllers

Views are returned from controller actions as a ViewResult, a type of ActionResult, using the View helper method:

HomeController.cs

public IActionResult About()
{
    ViewData["Message"] = "Your application description page.";

    return View(); // return a view with the same name as the action method from which it's called
}

The View helper method has some overloads:

return View(); // return a view with the same name as the action method from which it’s called
return View("Orders"); // return an explicit view
return View("Views/Home/About.cshtml"); // return an explicit view; the extension is required if using an absolute path
return View("../Manage/Index"); // return an explicit view inside a relative path
return View(Orders); // pass a model to the view
return View("Orders", Orders); // both a view and a model

View Discovery

When a controller action returns a view, view discovery occurs to determine which view file is used. This varies based on the View method overload used. View discovery searches Views/ControllerName then Views/Shared.