Building Your First Minimal API Using .NET 6 and C#

Introduction

Minimal API usage .NET and C# offer a fast, lightweight, and modern approach to building HTTP APIs using minimal configuration and boilerplate code. Introduced in .NET 6Minimal APIs are becoming increasingly popular microservices, cloud-native applicationAnd rapid prototyping because of its simplicity and performance. In this blog, you will learn how to create Minimal API step by step using .NET and C#set up an endpoint, and run your first lightweight API project.

Prerequisites for Building a Minimal API in .NET 6

Before starting, make sure you have:

• .NET SDK installed (version 6 or later)
• Code editor (Such as Visual Studio, VS Code, or JetBrains Rider)
• Basic knowledge about C#, REST APIAnd HTTP method

Create a Minimal API Using .NET 6 and C# Project Setup

Open your terminal or command prompt and create a new Minimal API project using the following command:

dotnet new web -n MinimalApiDemo

Basically, this command creates a new web project called MinimalApiDemo.

• Navigate to the Project Directory

cd MinimalApiDemo

• Open the Project in your Editor

In the next step, open the project in your favorite code editor to explore and work with the files.

Defining Models in a Minimal API

Let’s start by creating a simple model for a Todo item. In your project folder, create a new file called TodoItem.cs and add the code below:

public class TodoItem 
{ 
    public int Id { get; set; } 
    public string? Title { get; set; } 
    public bool IsCompleted { get; set; } 
} 

Setting Up an API Endpoint Using .NET 6 and C#

Now, let’s define an API endpoint that will handle various HTTP requests. To do this, open it Program.cs file and replace or update existing code with the example below:

var builder = WebApplication.CreateBuilder(args); 
var app = builder.Build(); 
 
List<TodoItem> todos = new(); 
 
app.MapGet("/todos", () => todos); 
 
app.MapGet("/todos/{id}", (int id) => 
    todos.FirstOrDefault(t => t.Id == id) 
); 
 
app.MapPost("/todos", (TodoItem todo) => 
{ 
    todo.Id = todos.Count + 1; 
    todos.Add(todo); 
    return Results.Created($"/todos/{todo.Id}", todo); 
}); 
 
app.MapPut("/todos/{id}", (int id, TodoItem updatedTodo) => 
{ 
    var todo = todos.FirstOrDefault(t => t.Id == id); 
    if (todo is null) return Results.NotFound(); 
 
    todo.Title = updatedTodo.Title; 
    todo.IsCompleted = updatedTodo.IsCompleted; 
 
    return Results.Ok(todo); 
}); 
 
app.MapDelete("/todos/{id}", (int id) => 
{ 
    var todo = todos.FirstOrDefault(t => t.Id == id); 
    if (todo is null) return Results.NotFound(); 
 
    todos.Remove(todo); 
    return Results.NoContent(); 
}); 
 
app.Run(); 

Code Explanation

Dependency Injection

We use a single list to store TodoItem object, providing a simple in-memory storage mechanism for demonstration purposes.

API Endpoint

• GET /all → Retrieve all plan items
• GET /todos/{id} → Get plan items by ID
• POST /all → Create a new plan item
• PLACE /todos/{id} → Update plan items
• DELETE /todos/{id} → Delete each item

Running APIs

Basically, to run the API, run the following command in your terminal:

dotnet run

Once the application is running, your API will be accessible at http://localhost:5000. You can test endpoints using tools like Postman or curly.

Running and Testing Minimal API

Sample Request

• Create a new Todo item using a POST request

curl -X POST  -H "Content-type: application/json" -d '{"title": "Learn Minimal APIs", "isCompleted": false}'

• Next, we will retrieve all Todo items using a GET request

curl -X GET /1 -H "Content-type: application/json" -d '{"title": "Learn Minimal APIs", "isCompleted": true}'

• Modify Existing Todo Items

curl -X PUT /1 -H "Content-type: application/json" -d '{"title": "Learn Minimal APIs", "isCompleted": true}'
curl -X DELETE /1
Conclusion
A minimal API using .NET provides a clean, fast, and efficient way to build small-scale services without the overhead of traditional controllers. They are perfect for microservices, cloud-native applications, prototypingand scenarios that prioritize performance and simplicity.
With just a few lines of C# code, you can create a fully functional endpoint, test it quickly, and scale from a simple demo to a production-ready service.
Whether you're a beginner or an experienced .NET developer, Minimal API is a powerful addition to your development toolkit.