Exercise - Create a to-do list

10 minutes

In this exercise, you use everything you learned so far to add a basic to-do list page to your Blazor app.

Create the to-do list page

Create a new Blazor Web App project.
Add a Todo.razor file to the Components/Pages folder

In Visual Studio and Visual Studio Code you can add the Razor file by right-clicking the Components/Pages folder in the Solution Explorer and selecting the appropriate option to add a new file.

You can also create the Razor file using the .NET CLI with this command:
```
dotnet new razorcomponent -n Todo -o Components/Pages
```
The -n|--name option in the preceding command specifies the name of the new Razor component. The new component is created in the project's Components/Pages folder with the -o|--output option.

Important

Razor component file names should have a capitalized first letter so they can easily be distinguished from other HTML elements.
Open the Todo component and add an @page Razor directive to the top of the file with a relative URL of /todo, and set the render mode to InteractiveServer so the component can handle UI events.
```
@page "/todo"
@rendermode InteractiveServer

<h3>Todo</h3>

@code {

}
```
Apply the changes to the app and try browsing to "/todo" to see your new page.

The new to-do list page doesn't yet appear in the nav menu with the other existing pages. The nav menu is defined in the NavMenu component, which is part of the app's layout. Let's update the NavMenu component to add a link to the to-do list page.

Open Components/Layout/NavMenu.razor.
Find the nav element in the NavMenu component and add the following div element below the existing nav item for the weather page.
```
<div class="nav-item px-3">
    <NavLink class="nav-link" href="todo">
        <span class="bi bi-list-nested-nav-menu" aria-hidden="true"></span> Todo
    </NavLink>
</div>
```
The NavLink component is a built-in Blazor component that renders an anchor tag. If the current browser address matches the href for the NavLink, it also renders an active CSS class that you can use for styling the link.

After applying this change, you should now see the Todo page show up in the nav menu.

Build a list of to-do items

Create a new TodoItem.cs file at the root of the project (the same level as Program.cs) and add the following C# class to it.
```
public class TodoItem
{
    public string? Title { get; set; }
    public bool IsDone { get; set; } = false;
}
```
In Todo.razor add a field for the list of to-do items in the @code block.
```
@code {
    private List<TodoItem> todos = new();
}
```
Render an unordered list of all the to-dos using a foreach loop.
```
<ul>
    @foreach (var todo in todos)
    {
        <li>@todo.Title</li>
    }
</ul>
```
You don't see anything rendered for the to-do list yet, because the list is empty. You need a way to add some to-do items.

Add to-do items

Let's add some UI elements for adding to-do items to our list.

In Todo.razor add an input tag and a button below the unordered list.
```
<input />
<button>Add todo</button>
```

Create a newTodo string field and bind it to the input using the @bind directive attribute.

<input @bind="newTodo" />
<button>Add todo</button>

@code {
    private List<TodoItem> todos = new();
    string newTodo = "";
}

Add a @onclick handler to the button that adds a new TodoItem to the todos list based on the value of newTodo and then resets the value of newTodo to an empty string.

<input @bind="newTodo" />
<button @onclick="AddTodo">Add todo</button>

@code {
    private List<TodoItem> todos = new();
    string newTodo = "";

    void AddTodo()
    {
        if (!string.IsNullOrWhiteSpace(newTodo))
        {
            todos.Add(new TodoItem { Title = newTodo });
            newTodo = string.Empty;
        }
    }
}

Check that you can now add to-do items and they show up in the list. The input value should also reset after adding each to-do item.

Add checkboxes and count incomplete to-do items

You need a way to mark to-do items as completed, to edit existing to-do items, and to count how many to-do items are yet to be done.

Update the contents of the li element to render an input of type checkbox that is bound to todo.IsDone and a text input that is bound to todo.Title.

<ul>
    @foreach (var todo in todos)
    {
        <li>
            <input type="checkbox" @bind="todo.IsDone" />
            <input @bind="todo.Title" />
        </li>
    }
</ul>

Update the <h3> header to show a count of the number of todo items that aren't complete (IsDone is false).
```
<h3>Todo (@todos.Count(todo => !todo.IsDone))</h3>
```

When you finish adding code, your Todo.razor file should resemble the following:

@page "/todo"
@rendermode InteractiveServer

<h3>Todo (@todos.Count(todo => !todo.IsDone))</h3>

<ul>
    @foreach (var todo in todos)
    {
        <li>
            <input type="checkbox" @bind="todo.IsDone" />
            <input @bind="todo.Title" />
        </li>
    }
</ul>

<input @bind="newTodo" />
<button @onclick="AddTodo">Add todo</button>

@code {
    private List<TodoItem> todos = new();
    string newTodo = "";

    void AddTodo()
    {
        if (!string.IsNullOrWhiteSpace(newTodo))
        {
            todos.Add(new TodoItem { Title = newTodo });
            newTodo = string.Empty;
        }
    }
}

After applying the changes to the app, try adding items, editing items, and marking todo items done to test the component.

Your Blazor to-do list is now done ✅.

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