.Net

1️⃣ What Is a Webhook?

A webhook is an automatic HTTP callback from one application to another.

Think of it like a doorbell:
- You don’t keep checking if someone is outside.
- Instead, the doorbell (webhook) notifies you immediately.

In software terms:

App A sends an HTTP POST request to a URL you provide whenever a specific event happens.
Your app receives the data instantly, without polling.

2️⃣ Real-Life Examples

Payment Gateway: Stripe or PayPal sends a webhook when a payment succeeds.
GitHub: Sends a webhook when someone pushes code to a repository.
Chat Apps: Slack sends a webhook when a new message arrives.

3️⃣ How It Works (Simple Flow)


Event Happens in Service A
        |
Service A sends HTTP POST (JSON)
        |
  Your Webhook Endpoint (Service B)
        |
   You process the data

Steps:

You give Service A a URL (e.g., https://yourapp.com/webhook/order).
Service A triggers an event (e.g., order created).
It sends a POST request with a JSON payload to your URL.
Your server reads it and takes action (update DB, send email, etc.).

4️⃣ Creating a Webhook Receiver in .NET

Here’s a minimal ASP.NET Core example:


[ApiController]
[Route("webhook")]
public class WebhookController : ControllerBase
{
    [HttpPost("order")]
    public async Task<IActionResult> Receive([FromBody] OrderEvent payload)
    {
        // Process the incoming event
        // e.g., save to database, trigger another service
        Console.WriteLine($"Order received: {payload.OrderId}");
        return Ok(); // Reply 200 so sender knows you got it
    }
}

public class OrderEvent
{
    public string OrderId { get; set; }
    public decimal Amount { get; set; }
}

Steps to use:

Deploy your app so it has a public HTTPS endpoint.
Give that URL to the service sending the webhook.
Test with a tool like ngrok (to expose local development) or Postman.

5️⃣ Sending a Webhook (If Your App Triggers One)

If you want to notify others:


using var http = new HttpClient();
await http.PostAsJsonAsync("https://partner.com/webhook/receive", new {
    OrderId = 123,
    Amount = 99.99M
});

6️⃣ Best Practices

Security: Verify signatures or use a secret token to ensure the request is genuine.
Retry/Idempotency: Handle duplicate messages—sender may retry if it doesn’t get a 200 OK.
Logging: Log every received event for debugging.
Timeouts: Reply quickly; heavy work should be queued or processed asynchronously.

7️⃣ Quick Recap

Webhook = “We push data to you when something happens.”
Sender: service that triggers the event.
Receiver: your endpoint that processes the POST request.
Great for real-time updates without constant polling.

In .NET, it’s just an ASP.NET Core controller action that accepts an HTTP POST with JSON.

Monday, 22 September 2025

Webhook