Azure Functions Binding Reference

This reference documentation provides details about the various triggers and bindings available for Azure Functions. Bindings allow you to declaratively connect your function to other Azure services and external data sources.

Core Concepts

Azure Functions uses a declarative binding model. You define inputs and outputs for your functions in the function.json file (or via attributes in code). This model simplifies your code by abstracting away the complexities of connecting to services.

Input and Output Bindings

Bindings can be categorized as:

• Input Bindings: Used to pass data into your function.
• Output Bindings: Used to send data from your function to another service.
• Trigger: A special type of input binding that starts your function's execution.

Supported Bindings

Below is a list of commonly used bindings. For a comprehensive list and detailed configurations, please refer to the specific service documentation.

HTTP Trigger and Output Bindings

The HTTP trigger starts your function in response to an HTTP request. The HTTP output binding allows your function to return an HTTP response.

{
  "scriptFile": "run.csx",
  "bindings": [
    {
      "authLevel": "function",
      "type": "httpTrigger",
      "direction": "in",
      "name": "req",
      "methods": [
        "get",
        "post"
      ]
    },
    {
      "type": "http",
      "direction": "out",
      "name": "res"
    }
  ]
}

using System.Net;
using Microsoft.Azure.WebJobs;
using Microsoft.Azure.WebJobs.Extensions.Http;
using Microsoft.Azure.WebJobs.Extensions.Rpc;
using Microsoft.AspNetCore.Http;
using Microsoft.Extensions.Logging;

public static class HttpExample
{
    [FunctionName("HttpExample")]
    public static async Task<IActionResult> Run(
        [HttpTrigger(AuthorizationLevel.Function, "get", "post", Route = null)] HttpRequest req,
        ILogger log)
    {
        log.LogInformation("C# HTTP trigger function processed a request.");

        string name = req.Query["name"];
        string requestBody = await new StreamReader(req.Body).ReadToEndAsync();
        dynamic data = JsonConvert.DeserializeObject(requestBody);
        string personName = data?.name ?? name;

        string responseMessage = string.IsNullOrEmpty(personName)
            ? "This HTTP triggered function executed successfully. Pass a name in the query string or in the request body for a personalized response."
            : $"Hello, {personName}!";

        return new OkObjectResult(responseMessage);
    }
}

Configuration Properties:

• type: Must be "httpTrigger" or "http".
• direction: "in" for trigger, "out" for output.
• name: The name of the parameter in your function code.
• methods (for trigger): Array of allowed HTTP methods (e.g., ["get", "post"]).
• route (optional): Custom route template.
• authLevel: Defines the authentication required ("anonymous", "function", "admin").

Timer Trigger

The Timer trigger executes your function based on a schedule.

{
  "scriptFile": "run.csx",
  "bindings": [
    {
      "type": "timerTrigger",
      "direction": "in",
      "name": "myTimer",
      "schedule": "0 */5 * * * *" // Runs every 5 minutes
    }
  ]
}

using System;
using Microsoft.Azure.WebJobs;
using Microsoft.Extensions.Logging;

public static class TimerExample
{
    [FunctionName("TimerExample")]
    public static void Run([TimerTrigger("0 */5 * * * *")]TimerInfo myTimer, ILogger log)
    {
        log.LogInformation($"C# Timer trigger function executed at: {DateTime.UtcNow}");
    }
}

Configuration Properties:

• type: Must be "timerTrigger".
• direction: Must be "in".
• name: The name of the parameter in your function code.
• schedule: A CRON expression defining the schedule.

Blob Storage Bindings

Interact with Azure Blob Storage for reading and writing data.

{
  "scriptFile": "run.csx",
  "bindings": [
    {
      "name": "inputBlob",
      "type": "blob",
      "direction": "in",
      "path": "samples-workitems/{name}.txt",
      "connection": "AzureWebJobsStorage"
    },
    {
      "name": "outputBlob",
      "type": "blob",
      "direction": "out",
      "path": "samples-output/{name}.txt",
      "connection": "AzureWebJobsStorage"
    }
  ]
}

using Microsoft.Azure.WebJobs;
using Microsoft.Extensions.Logging;

public static class BlobExample
{
    [FunctionName("BlobExample")]
    public static void Run(
        [BlobTrigger("samples-workitems/{name}.txt")] string inputBlob,
        [Blob("samples-output/{name}.txt", FileAccess.Write)] out string outputBlob,
        ILogger log)
    {
        log.LogInformation($"Blob input content: {inputBlob}");
        outputBlob = $"Processed: {inputBlob.ToUpper()}";
        log.LogInformation("Blob processed and output created.");
    }
}

Configuration Properties:

• type: Must be "blob".
• direction: "in" or "out".
• name: Parameter name.
• path: The container and blob name pattern (e.g., "input-container/{name}.txt").
• connection: Name of the app setting that contains the storage connection string.

Further Reading

• Overview of Azure Functions bindings
• Registering custom bindings