TODO Application Tutorial with Layered Solution

This is a single-part quick-start tutorial to build a simple todo application with the ABP. Here's a screenshot from the final application:

todo-list

You can find the source code of the completed application here.

This documentation has a video tutorial on YouTube!! You can watch it here:

Pre-Requirements

An IDE (e.g. Visual Studio) that supports .NET 8.0+ development.
Node v18.19+

Install ABP CLI Tool

We will use the ABP CLI to create new ABP solutions. You can run the following command on a terminal window to install this dotnet tool:

dotnet tool install -g Volo.Abp.Studio.Cli

Create Your ABP Solution

Create an empty folder, open a command-line terminal and execute the following command in the terminal:

abp new TodoApp -u blazor

This will create a new solution, named TodoApp. Once the solution is ready, open it in your favorite IDE.

Create the Database

If you are using Visual Studio, right click on the TodoApp.DbMigrator project, select Set as StartUp Project, then hit Ctrl+F5 to run it without debugging. It will create the initial database and seed the initial data.

Some IDEs (e.g. Rider) may have problems for the first run since DbMigrator adds the initial migration and re-compiles the project. In this case, open a command-line terminal in the folder of the .DbMigrator project and execute the dotnet run command.

Before Running the Application

Installing the Client-Side Packages

ABP CLI runs the abp install-libs command behind the scenes to install the required NPM packages for your solution while creating the application.

However, sometimes this command might need to be manually run. For example, you need to run this command, if you have cloned the application, or the resources from node_modules folder didn't copy to wwwroot/libs folder, or if you have added a new client-side package dependency to your solution.

For such cases, run the abp install-libs command on the root directory of your solution to install all required NPM packages:

abp install-libs

We suggest you install Yarn to prevent possible package inconsistencies, if you haven't installed it yet.

Bundling and Minification

abp bundle command offers bundling and minification support for client-side resources (JavaScript and CSS files) for Blazor projects. This command automatically run when you create a new solution with the ABP CLI.

However, sometimes you might need to run this command manually. To update script & style references without worrying about dependencies, ordering, etc. in a project, you can run this command in the directory of your blazor application:

abp bundle

For more details about managing style and script references in Blazor or MAUI Blazor apps, see Managing Global Scripts & Styles.

Run the Application

It is good to run the application before starting the development. The solution has two main applications;

TodoApp.HttpApi.Host hosts the server-side HTTP API.
TodoApp.Blazor is the client-side Blazor WebAssembly application.

Ensure the TodoApp.HttpApi.Host project is the startup project, then run the application (Ctrl+F5 in Visual Studio) to see the server-side HTTP API on the Swagger UI:

todo-swagger-ui-initial

You can explore and test your HTTP API with this UI. Now, we can set the TodoApp.Blazor as the startup project and run it to open the actual Blazor application UI:

todo-ui-initial

You can click on the Login button, use admin as the username and 1q2w3E* as the password to login to the application.

All ready. We can start coding!

Domain Layer

This application has a single entity and we'll start by creating it. Create a new TodoItem class inside the TodoApp.Domain project:

using System;
using Volo.Abp.Domain.Entities;

namespace TodoApp
{
    public class TodoItem : BasicAggregateRoot<Guid>
    {
        public string Text { get; set; } = string.Empty;
    }
}

BasicAggregateRoot is the simplest base class to create root entities, and Guid is the primary key (Id) of the entity here.

Database Integration

Next step is to setup the Entity Framework Core configuration.

Mapping Configuration

Open the TodoAppDbContext class in the EntityFrameworkCore folder of the TodoApp.EntityFrameworkCore project and add a new DbSet property to this class:

public DbSet<TodoItem> TodoItems { get; set; }

Then navigate to the OnModelCreating method in the TodoAppDbContext class and add the mapping code for the TodoItem entity:

protected override void OnModelCreating(ModelBuilder builder)
{
    base.OnModelCreating(builder);

    /* Include modules to your migration db context */

    builder.ConfigurePermissionManagement();
    ...

    /* Configure your own tables/entities inside here */
    builder.Entity<TodoItem>(b =>
    {
        b.ToTable("TodoItems");
    });
}

We've mapped the TodoItem entity to the TodoItems table in the database.

Code First Migrations

The startup solution is configured to use Entity Framework Core Code First Migrations. Since we've changed the database mapping configuration, we should create a new migration and apply changes to the database.

Open a command-line terminal in the directory of the TodoApp.EntityFrameworkCore project and type the following command:

dotnet ef migrations add Added_TodoItem

This will add a new migration class to the project:

todo-efcore-migration

You can apply changes to the database using the following command, in the same command-line terminal:

dotnet ef database update

If you are using Visual Studio, you may want to use the Add-Migration Added_TodoItem and Update-Database commands in the Package Manager Console (PMC). In this case, ensure that TodoApp.Blazor is the startup project and TodoApp.EntityFrameworkCore is the Default Project in PMC.

Now, we can use the ABP repositories to save and retrieve the todo items, as we'll do in the next section.

Application Layer

An Application Service is used to perform the use cases of the application. We need to perform the following use cases:

Get the list of the todo items
Create a new todo item
Delete an existing todo item

Application Service Interface

We can start by defining an interface for the application service. Create a new ITodoAppService interface in the TodoApp.Application.Contracts project, as shown below:

using System;
using System.Collections.Generic;
using System.Threading.Tasks;
using Volo.Abp.Application.Services;

namespace TodoApp
{
    public interface ITodoAppService : IApplicationService
    {
        Task<List<TodoItemDto>> GetListAsync();
        Task<TodoItemDto> CreateAsync(string text);
        Task DeleteAsync(Guid id);
    }
}

Data Transfer Object

GetListAsync and CreateAsync methods return TodoItemDto. ApplicationService typically gets and returns DTOs (Data Transfer Objects) instead of entities. So, we should define the DTO class here. Create a new TodoItemDto class inside the TodoApp.Application.Contracts project:

using System;

namespace TodoApp
{
    public class TodoItemDto
    {
        public Guid Id { get; set; }
        public string Text { get; set; } = string.Empty;
    }
}

This is a very simple DTO class that matches our TodoItem entity. We are ready to implement the ITodoAppService.

Application Service Implementation

Create a TodoAppService class inside the TodoApp.Application project, as shown below:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Volo.Abp.Application.Services;
using Volo.Abp.Domain.Repositories;

namespace TodoApp
{
    public class TodoAppService : ApplicationService, ITodoAppService
    {
        private readonly IRepository<TodoItem, Guid> _todoItemRepository;

        public TodoAppService(IRepository<TodoItem, Guid> todoItemRepository)
        {
            _todoItemRepository = todoItemRepository;
        }
        
        // TODO: Implement the methods here...
    }
}

This class inherits from the ApplicationService class of the ABP and implements the ITodoAppService that was defined before. ABP provides default generic repositories for the entities. We can use them to perform the fundamental database operations. This class injects IRepository<TodoItem, Guid>, which is the default repository for the TodoItem entity. We will use it to implement the use cases described before.

Getting Todo Items

Let's start by implementing the GetListAsync method:

public async Task<List<TodoItemDto>> GetListAsync()
{
    var items = await _todoItemRepository.GetListAsync();
    return items
        .Select(item => new TodoItemDto
        {
            Id = item.Id,
            Text = item.Text
        }).ToList();
}

We are simply getting the complete TodoItem list from the database, mapping them to TodoItemDto objects and returning as the result.

Creating a New Todo Item

Next method is CreateAsync and we can implement it as shown below:

public async Task<TodoItemDto> CreateAsync(string text)
{
    var todoItem = await _todoItemRepository.InsertAsync(
        new TodoItem {Text = text}
    );

    return new TodoItemDto
    {
        Id = todoItem.Id,
        Text = todoItem.Text
    };
}

The repository's InsertAsync method inserts the given TodoItem to the database and returns the same TodoItem object. It also sets the Id, so we can use it on the returning object. We are simply returning a TodoItemDto by creating from the new TodoItem entity.

Deleting a Todo Item

Finally, we can implement the DeleteAsync as the following code block:

public async Task DeleteAsync(Guid id)
{
    await _todoItemRepository.DeleteAsync(id);
}

The application service is ready to be used from the UI layer.

User Interface Layer

It is time to show the todo items on the UI! Before starting to write the code, it would be good to remember what we are trying to build. Here's a sample screenshot from the final UI:

todo-list

We will keep the UI side minimal for this tutorial to make the tutorial simple and focused. See the web application development tutorial to build real-life pages with all aspects.

Index.razor.cs

Open the Index.razor.cs file in the Pages folder of the TodoApp.Blazor project and replace the content with the following code block:

using Microsoft.AspNetCore.Components;
using System.Collections.Generic;
using System.Threading.Tasks;

namespace TodoApp.Blazor.Pages
{
    public partial class Index
    {
        [Inject]
        private ITodoAppService TodoAppService { get; set; }

        private List<TodoItemDto> TodoItems { get; set; } = new List<TodoItemDto>();
        private string NewTodoText { get; set; } = string.Empty;

        protected override async Task OnInitializedAsync()
        {
            TodoItems = await TodoAppService.GetListAsync();
        }
        
        private async Task Create()
        {
            var result = await TodoAppService.CreateAsync(NewTodoText);
            TodoItems.Add(result);
            NewTodoText = null;
        }

        private async Task Delete(TodoItemDto todoItem)
        {
            await TodoAppService.DeleteAsync(todoItem.Id);
            await Notify.Info("Deleted the todo item.");
            TodoItems.Remove(todoItem);
        }
    }
}

This class uses ITodoAppService to perform operations for the todo items. It manipulates the TodoItems list after create and delete operations. This way, we don't need to refresh the whole todo list from the server.

See the Dynamic C# Proxies & Auto API Controllers section below to learn how we could inject and use the application service interface from the Blazor application which is running on the browser! But now, let's continue and complete the application.

Index.razor

Open the Index.razor file in the Pages folder of the TodoApp.Blazor project and replace the content with the following code block:

@page "/"
@inherits TodoAppComponentBase
<div class="container">
    <Card>
        <CardHeader>
            <CardTitle>
                TODO LIST
            </CardTitle>
        </CardHeader>
        <CardBody>
            <!-- FORM FOR NEW TODO ITEMS -->
            <form id="NewItemForm" @onsubmit:preventDefault @onsubmit="() => Create()" class="row row-cols-lg-auto g-3 align-items-center">
                <div class="col-12">
                  <div class="input-group">
                    <input name="NewTodoText" type="text" @bind-value="@NewTodoText" class="form-control" placeholder="enter text..." />
                  </div>
                </div>
                <div class="col-12">
                  <button type="submit" class="btn btn-primary">Submit</button>
                </div>
            </form>
            <!-- TODO ITEMS LIST -->
            <ul id="TodoList">
                @foreach (var todoItem in TodoItems)
                {
                    <li data-id="@todoItem.Id">
                        <i class="far fa-trash-alt"
                           @onclick="() => Delete(todoItem)"
                           ></i> @todoItem.Text
                    </li>
                }
            </ul>
        </CardBody>
    </Card>
</div>

Index.razor.css

As the final touch, open the Index.razor.css file in the Pages folder of the TodoApp.Blazor project and replace it with the following content:

#TodoList{
    list-style: none;
    margin: 0;
    padding: 0;
}

#TodoList li {
    padding: 5px;
    margin: 5px 0px;
    border: 1px solid #cccccc;
    background-color: #f5f5f5;
}

#TodoList li i
{
    opacity: 0.5;
}

#TodoList li i:hover
{
    opacity: 1;
    color: #ff0000;
    cursor: pointer;
}

This is a simple styling for the todo page. We believe that you can do much better :)

Now, you can run the application again to see the result.

Dynamic C# Proxies & Auto API Controllers

In the Index.razor.cs file, we've injected (with the [Inject] attribute) and used the ITodoAppService just like using a local service. Remember that the Blazor application is running on the browser while the implementation of this application service is running on the server.

The magic is done by the ABP's Dynamic C# Client Proxy system. It uses the standard HttpClient and performs HTTP API requests to the remote server. It also handles all the standard tasks for us, including authorization, JSON serialization and exception handling.

However, you may ask that we haven't created any API Controller, so how does the server handle these requests? This question brings us to the Auto API Controller feature of the ABP. It automatically converts the application services to API Controllers by convention.

If you run the TodoApp.HttpApi.Host application, you can see the Todo API:

todo-api

Conclusion

In this tutorial, we've built a very simple application to warm up for the ABP. If you are looking to build a serious application, please check the web application development tutorial which covers all the aspects of real-life web application development.

Source Code

You can find source code of the completed application here.

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