Working with DELETE Method, Postman Testing, Entity Framework

This article builds on CRUD concepts (GET, POST, PUT, PATCH) and focuses on real-world API development with ASP.NET Core.

1. DELETE Method in ASP.NET Core Web API

What is DELETE?

The DELETE HTTP method is used to remove data from the server.

Real-life example:
Deleting a product from an online store's inventory.

Example Scenario: Delete a Product

Product Model

public class Product
{
    public int Id { get; set; }
    public string Name { get; set; }
    public decimal Price { get; set; }
}

API Code (DELETE)

[HttpDelete("{id}")]
public IActionResult DeleteProduct(int id)
{
    var product = products.FirstOrDefault(p => p.Id == id);
    if (product == null)
        return NotFound();

    products.Remove(product);
    return Ok($"Product with ID {id} deleted");
}

Input (Request)

DELETE /api/products/2

Output (Response)

"Product with ID 2 deleted"

After Deletion – GET Output

[
  { "id": 1, "name": "Laptop", "price": 1200 }
]

2. Testing Web API Using Postman (Step-by-Step)

What is Postman?

Postman is a tool used to test APIs by sending HTTP requests and viewing responses.

Step 1: Open Postman

Click New → HTTP Request

Step 2: Test GET

Method: GET
URL:

https://localhost:5001/api/products

Click Send
You will see JSON output.

Step 3: Test POST

Method: POST
URL:

https://localhost:5001/api/products

Body → Raw → JSON

{
  "name": "Keyboard",
  "price": 45
}

Click Send
New product is created.

Step 4: Test PUT

Method: PUT

https://localhost:5001/api/products/1

{
  "name": "Gaming Laptop",
  "price": 1500
}

Step 5: Test PATCH

Method: PATCH

https://localhost:5001/api/products/1

{
  "price": 1400
}

Step 6: Test DELETE

Method: DELETE

https://localhost:5001/api/products/1

3. Using Real Database with Entity Framework Core

What is Entity Framework Core?

EF Core is an Object Relational Mapper (ORM) that lets you work with databases using C# classes instead of SQL.

Step 1: Install Packages

dotnet add package Microsoft.EntityFrameworkCore.SqlServer
dotnet add package Microsoft.EntityFrameworkCore.Tools

Step 2: Create DbContext

using Microsoft.EntityFrameworkCore;

public class AppDbContext : DbContext
{
    public AppDbContext(DbContextOptions<AppDbContext> options)
        : base(options) { }

    public DbSet<Product> Products { get; set; }
}

Step 3: Configure in `Program.cs`

builder.Services.AddDbContext<AppDbContext>(options =>
    options.UseSqlServer(builder.Configuration.GetConnectionString("DefaultConnection")));

Step 4: Controller Using EF Core

[ApiController]
[Route("api/products")]
public class ProductsController : ControllerBase
{
    private readonly AppDbContext _context;

    public ProductsController(AppDbContext context)
    {
        _context = context;
    }

    [HttpGet]
    public IActionResult GetProducts()
    {
        return Ok(_context.Products.ToList());
    }

    [HttpPost]
    public IActionResult AddProduct(Product product)
    {
        _context.Products.Add(product);
        _context.SaveChanges();
        return Ok(product);
    }

    [HttpDelete("{id}")]
    public IActionResult DeleteProduct(int id)
    {
        var product = _context.Products.Find(id);
        if (product == null)
            return NotFound();

        _context.Products.Remove(product);
        _context.SaveChanges();
        return Ok("Deleted successfully");
    }
}

4. Interview-Ready Explanation (With Example)

Q1: What is the difference between GET and POST?

Answer:

GET retrieves data
POST sends data to create new records

Example:

GET /api/products → fetch products
POST /api/products → add product

Q2: Difference between PUT and PATCH?

Answer:

PUT updates the entire object
PATCH updates only specific fields

Q3: When do you use DELETE?

Answer:
DELETE is used to remove a resource permanently from the system.

Example:

DELETE /api/products/5

Q4: Why use Entity Framework Core?

Answer:

No need to write SQL
Faster development
Strongly typed data
Database-agnostic

Q5: How do you test APIs?

Answer:
Using tools like Postman or Swagger to send HTTP requests and verify responses.

Summary

Feature	Purpose
DELETE	Remove data
Postman	Test APIs
EF Core	Database operations
Interview Prep	Concept clarity

1. DELETE Method in ASP.NET Core Web API

What is DELETE?

Example Scenario: Delete a Product

API Code (DELETE)

Input (Request)

Output (Response)

After Deletion – GET Output

2. Testing Web API Using Postman (Step-by-Step)

What is Postman?

Step 1: Open Postman

Step 2: Test GET

Step 3: Test POST

Step 4: Test PUT

Step 5: Test PATCH

Step 6: Test DELETE

3. Using Real Database with Entity Framework Core

What is Entity Framework Core?

Step 1: Install Packages

Step 2: Create DbContext

Step 3: Configure in Program.cs

Step 4: Controller Using EF Core

4. Interview-Ready Explanation (With Example)

Q1: What is the difference between GET and POST?

Q2: Difference between PUT and PATCH?

Q3: When do you use DELETE?

Q4: Why use Entity Framework Core?

Q5: How do you test APIs?

Summary

Step 3: Configure in `Program.cs`