Build a Blazor todo list app

This tutorial provides a basic working experience for building and modifying a Blazor app. For detailed Blazor guidance, see the Blazor reference documentation.

Learn how to:

• Create a todo list Blazor app project
• Modify Razor components
• Use event handling and data binding in components
• Use routing in a Blazor app

At the end of this tutorial, you'll have a working todo list app.

Prerequisites

Download and install .NET if it isn't already installed on the system or if the system doesn't have the latest version installed.

Create a Blazor app

Create a new Blazor app named TodoList in a command shell:

dotnet new blazorserver -o TodoList

dotnet new blazorwasm -o TodoList

The preceding command creates a folder named TodoList with the -o|--output option to hold the app. The TodoList folder is the root folder of the project. Change directories to the TodoList folder with the following command:

cd TodoList

Build a todo list Blazor app

1. Add a new Todo Razor component to the app using the following command:

   dotnet new razorcomponent -n Todo -o 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 Pages folder with the -o|--output option.

   Important

   Razor component file names require a capitalized first letter. Open the Pages folder and confirm that the Todo component file name starts with a capital letter T. The file name should be Todo.razor.

2. Open the Todo component in any file editor and add an @page Razor directive to the top of the file with a relative URL of /todo.

   Pages/Todo.razor:

@page "/todo"

<PageTitle>Todo</PageTitle>

<h1>Todo</h1>

@code {

}

Save the Pages/Todo.razor file.

1. Add the Todo component to the navigation bar.

   The NavMenu component is used in the app's layout. Layouts are components that allow you to avoid duplication of content in an app. The NavLink component provides a cue in the app's UI when the component URL is loaded by the app.

   In the navigation element content (<nav class="flex-column">) of the NavMenu component, add the following <div> element for the Todo component.

   In Shared/NavMenu.razor:

<div class="nav-item px-3">
    <NavLink class="nav-link" href="todo">
        <span class="oi oi-list-rich" aria-hidden="true"></span> Todo
    </NavLink>
</div>

Save the Shared/NavMenu.razor file.

1. Build and run the app by executing the dotnet watch run command in the command shell from the TodoList folder. After the app is running, visit the new Todo page by selecting the Todo link in the app's navigation bar, which loads the page at /todo.

   Leave the app running the command shell. Each time a file is saved, the app is automatically rebuilt, and the page in the browser is automatically reloaded.

2. Add a TodoItem.cs file to the root of the project (the TodoList folder) to hold a class that represents a todo item. Use the following C# code for the TodoItem class.

   TodoItem.cs:

public class TodoItem
{
    public string? Title { get; set; }
    public bool IsDone { get; set; }
}

Note

If using Visual Studio to create the TodoItem.cs file and TodoItem class, use either of the following approaches:

• Remove the namespace that Visual Studio generates for the class.
• Use the Copy button in the preceding code block and replace the entire contents of the file that Visual Studio generates.

1. Return to the Todo component and perform the following tasks:

   • Add a field for the todo items in the @code block. The Todo component uses this field to maintain the state of the todo list.
   • Add unordered list markup and a foreach loop to render each todo item as a list item (<li>).

   Pages/Todo.razor:

@page "/todo"

<PageTitle>Todo</PageTitle>

<h1>Todo</h1>

<ul>
    @foreach (var todo in todos)
    {
        <li>@todo.Title</li>
    }
</ul>

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

1. The app requires UI elements for adding todo items to the list. Add a text input (<input>) and a button (<button>) below the unordered list (<ul>...</ul>):

@page "/todo"

<PageTitle>Todo</PageTitle>

<h1>Todo</h1>

<ul>
    @foreach (var todo in todos)
    {
        <li>@todo.Title</li>
    }
</ul>

<input placeholder="Something todo" />
<button>Add todo</button>

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

1. Save the TodoItem.cs file and the updated Pages/Todo.razor file. In the command shell, the app is automatically rebuilt when the files are saved. The browser reloads the page.

2. When the Add todo button is selected, nothing happens because an event handler isn't attached to the button.

3. Add an AddTodo method to the Todo component and register the method for the button using the @onclick attribute. The AddTodo C# method is called when the button is selected:

<input placeholder="Something todo" />
<button @onclick="AddTodo">Add todo</button>

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

    private void AddTodo()
    {
        // Todo: Add the todo
    }
}

1. To get the title of the new todo item, add a newTodo string field at the top of the @code block:

private string? newTodo;

Modify the text <input> element to bind newTodo with the @bind attribute:

<input placeholder="Something todo" @bind="newTodo" />

1. Update the AddTodo method to add the TodoItem with the specified title to the list. Clear the value of the text input by setting newTodo to an empty string:

@page "/todo"

<PageTitle>Todo</PageTitle>

<h1>Todo</h1>

<ul>
    @foreach (var todo in todos)
    {
        <li>@todo.Title</li>
    }
</ul>

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

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

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

1. Save the Pages/Todo.razor file. The app is automatically rebuilt in the command shell, and the page reloads in the browser.

2. The title text for each todo item can be made editable, and a checkbox can help the user keep track of completed items. Add a checkbox input for each todo item and bind its value to the IsDone property. Change @todo.Title to an <input> element bound to todo.Title with @bind:

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

3. Update the <h1> header to show a count of the number of todo items that aren't complete (IsDone is false). The Razor expression in the following header evaluates each time Blazor rerenders the component.

   <h1>Todo (@todos.Count(todo => !todo.IsDone))</h1>
   

4. The completed Todo component (Pages/Todo.razor):

@page "/todo"

<PageTitle>Todo</PageTitle>

<h1>Todo (@todos.Count(todo => !todo.IsDone))</h1>

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

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

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

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

1. Save the Pages/Todo.razor file. The app is automatically rebuilt in the command shell, and the page reloads in the browser.

2. Add items, edit items, and mark todo items done to test the component.

3. When finished, shut down the app in the command shell. Many command shells accept the keyboard command Ctrl+C (Windows) or ⌘+C (macOS) to stop an app.

Publish to Azure

For information on deploying to Azure, see Quickstart: Deploy an ASP.NET web app.

Next steps

In this tutorial, you learned how to:

• Create a todo list Blazor app project
• Modify Razor components
• Use event handling and data binding in components
• Use routing in a Blazor app

Learn about tooling for ASP.NET Core Blazor:

ASP.NET Core Blazor