Serverless computing is revolutionizing the way developers build and scale applications — and Azure Functions are at the heart of this shift in the Microsoft ecosystem. These lightweight, event-driven components let you run code without provisioning or managing infrastructure. In this blog, we’ll explore 7 essential Azure Function triggers, each explained with a real-world scenario and C# sample code.
Azure Function Triggers
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HTTP Trigger Function — Build Lightweight APIs
An HTTP Trigger Function enables you to create RESTful endpoints that respond to HTTP GET or POST requests — perfect for APIs, form submissions, or integrations.
Sample Use Case: Hello API
[FunctionName("HttpTriggerExample")]
public static IActionResult Run(
[HttpTrigger(AuthorizationLevel.Function, "get", "post")] HttpRequest req)
{
string name = req.Query["name"];
return new OkObjectResult($"Hello, {name}!");
}Timer Trigger Function—Scheduled Jobs (CRON)
Timer triggers are ideal for automating background jobs like daily reports, reminders, or data cleanups using a CRON expression.
Real Use Case: Daily Sales Report at 7:00 AM
[FunctionName("DailySalesReport")]
public static async Task Run(
[TimerTrigger("0 0 7 * * *")] TimerInfo myTimer,
ILogger log)
{
log.LogInformation($"Function executed at: {DateTime.UtcNow}");
var salesData = await GetDailySalesDataAsync();
var report = GenerateReport(salesData);
await SendEmailAsync(report);
}CRON Expression Format
| Expression | Description |
|---|---|
0 */5 * * * * |
Every 5 minutes |
0 0 7 * * * |
Every day at 7 AM UTC |
0 0 9 * * 1 |
Every Monday at 9 AM UTC |
Queue Trigger Function—Asynchronous Processing
Queue triggers let you respond to new messages in Azure Storage Queues, ideal for order processing, background jobs, or email sending.
Sample Use Case: Order Fulfillment
[FunctionName("ProcessOrder")]
public static async Task Run(
[QueueTrigger("orders-queue", Connection = "AzureWebJobsStorage")] string orderMessage,
ILogger log)
{
var order = JsonConvert.DeserializeObject<Order>(orderMessage);
log.LogInformation($"Processing order #{order.OrderId} for {order.CustomerName}");
await Task.Delay(2000); // simulate work
}Blob Trigger Function — File-Based Workflows
Blob triggers automatically run when a new file (e.g. PDF, image) is uploaded to Azure Blob Storage — excellent for document processing, image resizing, or metadata extraction.
Use Case: Invoice Processing
[FunctionName("ProcessInvoice")]
public static async Task Run(
[BlobTrigger("invoices/{name}", Connection = "AzureWebJobsStorage")] Stream invoiceBlob,
string name,
ILogger log)
{
using var reader = new StreamReader(invoiceBlob);
string fileContent = await reader.ReadToEndAsync();
log.LogInformation($"Invoice '{name}' read with {fileContent.Length} characters");
}Event Grid Trigger Function — Event-Driven Architecture
Azure Event Grid lets you build real-time, event-driven solutions that react to Azure resource changes, blob uploads, or custom events.
Use Case: Auto-Archive Deallocated VMs
[FunctionName("VMDeallocationEventHandler")]
public static async Task Run(
[EventGridTrigger] EventGridEvent eventGridEvent,
ILogger log)
{
JObject data = eventGridEvent.Data as JObject;
string vmName = data["resource"]?.ToString();
log.LogInformation($"Archiving VM: {vmName}");
await Task.Delay(500); // simulate archive
}Orchestration Function (Durable) — Manage Complex Workflows
Durable Functions let you orchestrate workflows by chaining multiple functions together, maintaining state and ensuring reliability even across retries and restarts.
Use Case: Order Workflow
Orchestrator:
[FunctionName("OrderOrchestrator")]
public async Task RunOrchestrator(
[OrchestrationTrigger] IDurableOrchestrationContext context)
{
var orderId = context.GetInput<string>();
await context.CallActivityAsync("ValidateOrder", orderId);
await context.CallActivityAsync("ProcessPayment", orderId);
await context.CallActivityAsync("SendConfirmationEmail", orderId);
}Activity Functions:
[FunctionName("ValidateOrder")]
public Task ValidateOrder([ActivityTrigger] string orderId, ILogger log) =>
Task.CompletedTask;HTTP Starter:
[FunctionName("StartOrderProcessing")]
public async Task<HttpResponseMessage> Start(
[HttpTrigger(AuthorizationLevel.Function, "post")] HttpRequestMessage req,
[DurableClient] IDurableOrchestrationClient starter,
ILogger log)
{
var orderId = await req.Content.ReadAsStringAsync();
string instanceId = await starter.StartNewAsync("OrderOrchestrator", orderId);
return starter.CreateCheckStatusResponse(req, instanceId);
}Cosmos DB Trigger — Real-Time Data Processing
React to insert, update, or delete operations in your Cosmos DB collection. Great for syncing changes, sending notifications, or triggering data pipelines.
Use Case: Process Document Changes
[FunctionName("CosmosDBChangeHandler")]
public static void Run(
[CosmosDBTrigger(
databaseName: "YourDatabaseName",
collectionName: "YourCollectionName",
ConnectionStringSetting = "CosmosDBConnectionString",
LeaseCollectionName = "leases",
CreateLeaseCollectionIfNotExists = true)] IReadOnlyList<Document> documents,
ILogger log)
{
foreach (var document in documents)
{
log.LogInformation($"Document changed: {document.GetPropertyValue<string>("id")}");
}
}How to Create and Deploy Azure Functions
1. Create a Function App in the Azure Portal
2. Choose Your Trigger Type (HTTP, Timer, etc.)
3. Write & Deploy Code via Azure Portal or Visual Studio Code
4. Monitor Logs & Execution in the Monitor tab
Limitations of Azure Functions
- Cold Starts: Can be slow on the first call.
- Timeouts: Consumption plan limits (5 minutes default, 60 max).
- State Management: Must use Durable Functions or external storage.
- Vendor Lock-In: Heavily tied to Azure ecosystem.
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Conclusion
Azure Functions offer a cost-effective, scalable, and developer-friendly approach to building serverless applications. From APIs and scheduled jobs to workflow orchestration and real-time event processing, they allow you to focus on business logic while Azure handles the rest.
Whether you’re building your first function or designing a complex distributed system, Azure Functions can dramatically accelerate your cloud journey.
