Getting Started with ASP.NET Core Web API: A Beginner's Guide

Introduction

In this blog, you’ll learn how to create a simple ASP.NET Core Web API from scratch using Visual Studio. This step-by-step guide is perfect for beginners looking to understand how RESTful APIs work.

What is a Web API?

A Web API(Application Programming Interface) allows different applications to communicate with each other over HTTP and is used to build RESTful services.

Why do we use ASP.NET Core Web API?

• Cross-platform(Platform Independent)
• Supports DI(Depenency Injection)
• Supports OpenAI(Swagger)

Prerequisites

• Basic knowledge of C# and SQL
• .NET SDK
• Familiar with Visual Studio IDE

Creating your first Web API project

Step 1

• Open Visual Studio
• Create a new project
• Select the ASP.NET Core Web API template

Step 2

• Name it EmployeeManagement
• Choose the latest .NET version
• Click Create

Understanding the Code Structure

• Program.cs: Entry point for application
• Controllers: Contains API controllers
• Models: Contains business logic
• appsettings.json: Configuration file

DbContext Setup with SQL Server

• To make your API data persistent, you can connect it to a SQL Server database using Entity Framework Core.
• First, install the required EF Core packages that support SQL Server. Then, create a class called EmployeeDbContext that manages database access and maps your Employee model to a database table.
• Next, register this DbContext in the application’s services so that it can be used in the controller. You'll also add a connection string in the configuration file (appsettings.json) to define how the app connects to SQL Server.

CRUD Operations for Employee

Create the Model: Models/Entities/Employee.cs.

Create the Controller: Controllers/EmployeesController.cs

1. GET – Get All Employees & Get by ID

These two methods handle the retrieval of employee data.

• The first method [HttpGet] returns a full list of employees with an HTTP 200 OK response.
• The second method [HttpGet("{id}")] retrieves a specific employee by ID.

2. POST – Add a New Employee

This method handles employee creation.

• The [HttpPost] method accepts an Employee object from the request body.
• It adds the employee to the database.

3. PUT – Update an Existing Employee

This method updates the details of an existing employee

• The [HttpPut("{id}")] method checks if an employee with the given ID exists.
• It updates the employee’s name, department, phone, and salary.

4. DELETE – Remove an Employee

This method deletes an employee based on the provided ID.

• The [HttpDelete("{id}")] method searches for the employee.
• If the employee exists, it removes them from the list.

Testing with Swagger

https://localhost:{port}/swagger/index.html

You can test all GET, POST, PUT, and DELETE requests directly from the Swagger interface.

Conclusion

In this blog, you learned how to build a simple yet functional Employee Management Web API using ASP.NET Core. We covered how to create models, set up controllers, implement CRUD operations, and connect to a SQL Server database using Entity Framework Core.

Source Code

You can find the complete source code for this project on GitHub using the link below.

GitHub Repo: https://github.com/Vinay-Reddy-Thadakala/EmployeeManagement