📓 Applying RESTful Routing

In the last lesson, we covered RESTful principles. In this lesson, we'll continue developing our application following RESTful routing best practices. First, we'll update our existing CreateForm() route to follow RESTful convention. Then we'll add a Show() route to display a detail page for individual Items.

`New()` Route

Existing Index() and Create() routes in our ItemsController already match RESTful convention, as we can see by comparing our controller code to the table in the previous lesson. However, CreateForm() does not. It currently looks like this:

ToDoList/Controllers/ItemsController.cs

...

  [HttpGet("/items/new")]
  public ActionResult CreateForm()
  {
    return View();
  }

...

Let's also compare it to the table in the last lesson:

Route Name: This method is called CreateForm(). In order to adhere to RESTful convention, it should be named New().
URL Path: The path is "items/new". This already follows RESTful convention because it lists the plural model name (Items), alongside /new, which indicates to others that this route contains the necessary materials (a form) to create a new instance of the model (Item).
HTTP Method: HttpGet() is used in the route decorator, which properly signifies that this route handles GET requests.
Purpose: Our route returns a view with a form to create a new instance of the Item model.

The only thing we need to change is the route name. We'll rename CreateForm() to New():

ToDoList/Controllers/ItemsController.cs

...

  [HttpGet("/items/new")]
  public ActionResult New()
  {
    return View();
  }

...

Because the View() method will automatically look for a .cshtml view with the same name, we must also rename our existing CreateForm.cshtml file to New.cshtml:

ToDoList/Views/Items/New.cshtml

<!DOCTYPE html>
<html>
  <head>
    <meta charset="utf-8">
    <title>My To-Do List!</title>
    <link 
      href="https://cdn.jsdelivr.net/npm/bootstrap@5.2.3/dist/css/bootstrap.min.css" 
      rel="stylesheet" 
      integrity="sha384-rbsA2VBKQhggwzxH7pPCaAqO46MgnOM80zW1RWuH61DGLwZJEdK2Kadq2F9CUG65" 
      crossorigin="anonymous">
  </head>
  <body>
    <form action="/items" method="post">
      <label for="description">Add a new item</label>
      <input id="description" name="description" type="text">
      <button type="submit">Submit</button>
    </form>
  </body>
</html>

Item Detail Page

The RESTful `Show()` Route

Now let's add a detail page so users can click an individual Item in our Items/Index.cshtml view to navigate to a page displaying details about that Item.

Navigating to the Route

First, we'll ensure users have a way to access this page. Let's update our existing Items/Index.cshtml view so each Item in our list is a link to that Item's detail page:

ToDoList/Views/Items/Index.cshtml

...

  <li><a href='/items/@item.Id'>@item.Description</a></li>

...

Here we're creating a link. Since this link needs to work for all Items, we use the Razor statement @item.Id directly in the href property of the <a> tag. If an Item has an Id of 565, the link will read /items/565, and so on.

The entire updated file looks like this:

ToDoList/Views/Items/Index.cshtml

<!DOCTYPE html>
<html>
  <head>
    <meta charset="utf-8">
    <title>My To-Do List!</title>
    <link 
      href="https://cdn.jsdelivr.net/npm/bootstrap@5.2.3/dist/css/bootstrap.min.css" 
      rel="stylesheet" 
      integrity="sha384-rbsA2VBKQhggwzxH7pPCaAqO46MgnOM80zW1RWuH61DGLwZJEdK2Kadq2F9CUG65" 
      crossorigin="anonymous">
  </head>
  <body>
    @using ToDoList.Models;

    <h1>To Do List</h1>
    @if (Model.Count == 0)
    {
      <p>There are no items in the list.</p>
    }
    <ul>
      @foreach (Item item in Model)
      {
        <li><a href='/items/@item.Id'>@item.Description</a></li>
      }
    </ul>

    <a href="/items/new">Add a new item.</a>

    <form action="/items/delete" method="post">
      <button type="submit" name="button">Clear All Items</button>
    </form>
  </body>
</html>

Route Method

Now we need to create our route to handle these requests. Let's plan how we'll make our new route RESTful:

Route Name: It will be called Show().
URL Path: The path should be "items/{id}", where {id} is a placeholder for the specific Item we're currently looking at. We'll discuss this further in a moment.
HTTP Method: The request to view the detail page will be a GET request, so it will use HttpGet() in its route decorator.
Purpose: It will be responsible for rendering a detail page for a specific Item.

Now that we've created a plan, we're ready to add the code for our route.

ToDoList/Controllers/ItemsController.cs

...

    [HttpGet("/items/{id}")]
    public ActionResult Show(int id)
    {
      Item foundItem = Item.Find(id);
      return View(foundItem);
    }

...

We have some new syntax: curly braces in the URL path in our route decorator. Our route is now utilizing dynamic routing.

Dynamic Routing

Dynamic Routing refers to routes and their URL paths that can dynamically change depending on circumstances. A common example is an id like in the example above.

The {id} portion of the path is a placeholder. Remember, this route will be invoked for viewing any Item's detail page.
Our link in Index.cshtml looks like this: <a href='/items/@item.Id'>. For example, if we click on an Item with an id of 42, the path will be "/items/42". When that occurs, {id} will represent 42.
This same id is passed into the Show() route method as a parameter. The method takes an int argument named id, which is the same id from the path.
Once Show() has access to the id as a parameter, it can pass this value into Find() to locate the Item matching this id.
The route can then pass this entire Item object into View(), so the corresponding view may access and render its information.

Note on Dynamic Route Segment Names

Note that the term id is nothing magical here. We could rewrite the route like this:

 [HttpGet("/items/{aReallyExcitingOneOfAKindIdNumber}")]
 public ActionResult Show(int aReallyExcitingOneOfAKindIdNumber)
 {
   Item foundItem = Item.Find(aReallyExcitingOneOfAKindIdNumber);
   return View(foundItem);
 }

This would still work as long as the named segment in the URL path and parameter provided to the route match. However, id is standard and our variable names should always be concise and descriptive.

Detail View

Because our new dynamic route returns View(foundItem), it will look for a view file with the same name as our route method. Our Show() method exists on the ItemsController, so we'll create a Show.cshtml view file in the Views/Items directory with the following code:

ToDoList/Views/Items/Show.cshtml

<!DOCTYPE html>
<html>
  <head>
    <meta charset="utf-8">
    <title>My To-Do List!</title>
    <link 
      href="https://cdn.jsdelivr.net/npm/bootstrap@5.2.3/dist/css/bootstrap.min.css" 
      rel="stylesheet" 
      integrity="sha384-rbsA2VBKQhggwzxH7pPCaAqO46MgnOM80zW1RWuH61DGLwZJEdK2Kadq2F9CUG65" 
      crossorigin="anonymous">
  </head>
  <body>
    <h1>To Do List Item Details: </h1>

    <h2>@Model.Description</h2>

    <a href='/items/new'>Add another item</a>
    <a href='/items'>View all items</a>
  </body>
</html>

When we run our application now, we can populate it with several Items and click an Item from the /items page to navigate to a detail page with that item's specific information.

Repository Reference

Follow the link below to view how a sample version of the project should look at this point. Note that this is a link to a specific branch in the repository.

Example GitHub Repo for To Do List: 6_applying_restful_routing

New() Route​

Item Detail Page​

The RESTful Show() Route​

Navigating to the Route​

Route Method​

Dynamic Routing​

Note on Dynamic Route Segment Names​

Detail View​

Repository Reference​

`New()` Route

Item Detail Page

The RESTful `Show()` Route

Navigating to the Route

Route Method

Dynamic Routing

Note on Dynamic Route Segment Names

Detail View

Repository Reference