.Net: Azure Function

💡 What is an Azure Function?

Azure Functions is a serverless compute service.

You write small pieces of code (“functions”) that run on demand.
Microsoft manages all the servers, scaling, and infrastructure.
You pay only for the execution time.

🚀 Key Features

Event-driven: Triggered by events like HTTP requests, a queue message, a timer, or a blob upload.
Automatic scaling: Runs as many instances as needed.
Multiple triggers & bindings: Connect to storage, Service Bus, Cosmos DB, etc.

🏗️ Create a Simple HTTP-Triggered Function (C#)

1️⃣ Prerequisites

.NET 6/7/8 SDK (latest recommended)
Azure Functions Core Tools
Visual Studio 2022 or VS Code with Azure Functions extension
Azure subscription (for deployment)

2️⃣ Create the Project

With Visual Studio:

New Project → Azure Functions → Next.
Name it, choose .NET 6/7/8 (Isolated or In-Process).
Choose Trigger type = HTTP Trigger.
Authorization level: Anonymous (for testing).

This generates a default function file like:


using System.Net;

public static class HelloFunction
{
    [FunctionName("HelloFunction")]
    public static IActionResult Run(
        [HttpTrigger(AuthorizationLevel.Function, "get", "post")] HttpRequest req,
        ILogger log)
    {
        log.LogInformation("C# HTTP trigger function processed a request.");

        string name = req.Query["name"];
        return new OkObjectResult($"Hello, {name ?? "world"}!");
    }
}

3️⃣ Run Locally

Press F5 (Visual Studio) or use CLI:
```
func start
```
Test in browser:
http://localhost:7071/api/HelloFunction?name=Shivan

4️⃣ Deploy to Azure

Right-click project → Publish → Azure.
Choose an existing or new Function App in your Azure subscription.
After deployment, Azure gives you a public URL.

⏱️ Other Common Triggers

Timer Trigger: Run on a schedule (like a cron job).
Queue/Service Bus Trigger: Run when a message arrives.
Blob Trigger: Run when a file is uploaded to Azure Storage.

Example Timer Trigger:


[FunctionName("DailyCleanup")]
public static void Run([TimerTrigger("0 0 2 * * *")]TimerInfo myTimer, ILogger log)
{
    log.LogInformation($"Cleanup executed at: {DateTime.Now}");
}

🔌 Input and Output Bindings

Bindings connect your function to other services with minimal code.

Example: Save an HTTP request body to Cosmos DB


[FunctionName("SaveOrder")]
public static async Task<IActionResult> Run(
    [HttpTrigger("post")] HttpRequest req,
    [CosmosDB(
        databaseName: "OrdersDb",
        containerName: "Orders",
        Connection = "CosmosDBConnection")] IAsyncCollector<Order> ordersOut,
    ILogger log)
{
    var order = await JsonSerializer.DeserializeAsync<Order>(req.Body);
    await ordersOut.AddAsync(order);
    return new OkResult();
}

No explicit Cosmos client code required—Azure handles it.

⚙️ Hosting Plans

Consumption (default): Pay per execution, scales automatically.
Premium: Always warm, more performance.
Dedicated (App Service Plan): Fixed compute, for special cases.

✅ Key Points

Event-driven & serverless → write only the logic.
Supports many triggers/bindings (HTTP, Timer, Queue, Blob, Event Grid, etc.).
Write in C# (in-process or isolated process) with .NET 6/7/8.
Local dev → test → deploy to Azure with one command.

🏁 Summary

An Azure Function in C# is just a small method decorated with a [FunctionName] attribute that responds to a trigger (HTTP, Timer, Queue, etc.).
You:

Create a Function project,
Write the function logic,
Run locally and deploy.

This makes it perfect for microservices, scheduled jobs, or quick API endpoints without managing servers.

.Net

Monday, 22 September 2025

Azure Function