? Building a Todo List API with .NET Core Minimal APIs ? A Simple & Powerful Guide

[Lomanu4]

? .NET Core's Minimal APIs offer a streamlined approach to building HTTP APIs with reduced boilerplate. This post walks you through creating a Todo list API from scratch, showcasing the simplicity and power of Minimal APIs.

Prerequisites

• .NET Core SDK (latest version recommended)
• A code editor (VS Code, JetBrains Rider, etc.)
• Basic understanding of C# and RESTful API concepts
• Visual Studio 2022 or later (for using Endpoints Explorer)

Project Setup

1. 
   Create a new Web API project:
   
   dotnet new webapi -o MinimalTodoApi
   cd MinimalTodoApi
2. 
   Install Entity Framework Core packages:
   
   We'll use EF Core for data persistence. Install the necessary packages:
   
   dotnet add package Microsoft.EntityFrameworkCore.SqlServer # Or your preferred database provider
   dotnet add package Microsoft.EntityFrameworkCore.Design
   dotnet add package Microsoft.EntityFrameworkCore.Tools

Defining the Todo Model


Create a Models directory and add a Todo.cs file:


namespace MinimalTodoApi.Models;

public class Todo
{
// Unique identifier for the Todo item
public Guid Id { get; set; }

// Name or description of the Todo item
public string? Name { get; set; }

// Indicates whether the Todo item is complete
public bool IsComplete { get; set; }
}

This simple model defines the structure of our Todo items.

Setting up the Database Context


Create a Data directory and add TodoDb.cs:


using Microsoft.EntityFrameworkCore;
using MinimalTodoApi.Models;

namespace MinimalTodoApi.Data;

// Represents the database context for the Todo application
public class TodoDb : DbContext
{
// Constructor that accepts DbContextOptions
public TodoDb(DbContextOptions<TodoDb> options) : base(options) { }

// Represents the collection of Todo items in the database
public DbSet<Todo> Todos { get; set; }
}

This class sets up our database context using Entity Framework Core.

Configuring the Minimal API Endpoints (Program.cs)


Now, let's define our API endpoints within Program.cs:


using Microsoft.EntityFrameworkCore;
using MinimalTodoApi.Data;
using MinimalTodoApi.Models;

var builder = WebApplication.CreateBuilder(args);

// Add the database context to the services container. This allows the database to be injected into the API endpoints.
builder.Services.AddDbContext<TodoDb>(options
=> options.UseSqlServer(builder.Configuration.GetConnectionString("MinimalTodo"))
);

var app = builder.Build();

// Configure the API endpoints

// Get all todo items
app.MapGet("/todos", async (TodoDb db) =>
await db.Todos.ToListAsync());

// Get completed todo items
app.MapGet("/todos/complete", async (TodoDb db) =>
await db.Todos.Where(t => t.IsComplete).ToListAsync());

// Get a specific todo item by ID
app.MapGet("/todos/{id}", async (Guid id, TodoDb db) =>
await db.Todos.FindAsync(id)
is Todo todo
? Results.Ok(todo)
: Results.NotFound());

// Create a new todo item
app.MapPost("/todos", async (Todo todo, TodoDb db) =>
{
db.Todos.Add(todo);
await db.SaveChangesAsync();

return Results.Created($"/todos/{todo.Id}", todo);
});

// Update an existing todo item
app.MapPut("/todos/{id}", async (Guid id, Todo inputTodo, TodoDb db) =>
{
var todo = await db.Todos.FindAsync(id);
if (todo is null) return Results.NotFound();

todo.Name = inputTodo.Name;
todo.IsComplete = inputTodo.IsComplete;
await db.SaveChangesAsync();
return Results.NoContent();
});

// Delete a todo item
app.MapDelete("/todos/{id}", async (Guid id, TodoDb db) =>
{
if (await db.Todos.FindAsync(id) is Todo todo)
{
db.Todos.Remove(todo);
await db.SaveChangesAsync();
return Results.NoContent();
}
return Results.NotFound();
});

app.Run();

Key improvements and explanations:

• Clear separation of concerns: Models in Models, database context in Data.
• Concise endpoint definitions: Minimal APIs make routing and logic clear.
• Dependency Injection: The TodoDb context is injected directly into the endpoint handlers.
• Asynchronous operations: Using async and await for non-blocking database calls.

Database Configuration

1. 
   Update appsettings.json:
   
   Configure your database connection string. For example, using SQL Server:
   
   {
   "Logging": {
   "LogLevel": {
   "Default": "Information",
   "Microsoft.AspNetCore": "Warning"
   }
   },
   "ConnectionStrings": {
   "MinimalTodo": "Server=(localdb)\\mssqllocaldb;Database=MinimalTodo;Trusted_Connection=True;MultipleActiveResultSets=true"
   },
   "AllowedHosts": "*"
   }
2. 
   Create and apply migrations:
   
   dotnet ef migrations add InitialCreate
   dotnet ef database update

Running the API


dotnet run

Your Todo API is now running!

Testing the API with Endpoints Explorer (Visual Studio)


Visual Studio provides a built-in tool to explore and test your API endpoints:

1. Open Endpoints Explorer: In Visual Studio, go to View > Other Windows > Endpoints Explorer.
2. Locate your API endpoints: The Endpoints Explorer will display a list of all available API endpoints in your project. You should see the /todos endpoints listed.
3. Test the endpoints: You can right-click on an endpoint and select "Generate Request" to create a sample HTTP request. Modify the request as needed (e.g., add a request body for POST/PUT requests) and then click "Send Request" to test the endpoint. The response will be displayed in a separate window.

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Conclusion


.NET Core Minimal APIs provide a powerful and elegant way to build APIs with minimal code. This Todo list example demonstrates the core concepts and provides a foundation for building more complex applications. Embrace the simplicity and efficiency of Minimal APIs in your next .NET project!

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